Just got a Bonneville of my own and wanted to know some quicker and cheaper mods I could slap onto it. I’m still a student so the most expensive mod I’m considering is ZZP’s H-Body down pipe with cat. Also considering a K&N drop in filter and a 180° thermostat. I know y’all are a lot more experienced so wanted to know your thoughts on the ease and gains of these mods and other one! Also very curious about aftermarket suspension. Thank you!

I might get some flack for this, but I used to be in your shoes as a student with a limited budget. This is a terrible platform for performance in every sense, and starting with an NA car only makes it worse. Almost nothing makes a noticeable difference in power. The HP per $ ratio is awful. If you really want more power, you need to boost it from the start. But then you're still going to be stuck with a terrible trans made of glass with terrible gearing powering the wrong wheels.

I would recommend saving your money and doing all of the important maintenance items such as lower intake gaskets, upper intake, coolant elbows, addressing interior water leaks, changing fluids, and keeping an eye on rust. Check out the 2000-2005 section for the common problems thread for a great start.
Save your money for a platform/vehicle that actually makes sense to modify. Keep the Bonneville as a daily driver. They are hard to beat for comfort, generally decent fuel economy, ease of maintenance and cheap parts.

There is no aftermarket suspension available. GXP parts used to be an upgrade but they are no longer possible to find in any decent sort of shape. You might be able to find some GXP sway bars, and those don't theoretically wear out. The rest of the suspension is unique to the GXP, and this age and most of their mileage, it is trash. The strut bar does nothing by the way...

Sorry to be a buzzkill. Lol

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-Car Guy Carl
"Penelope" - 2003 SLE - 247k Miles
"Sydney" - 2000 Honda S2000 - 98k miles

Really appreciate it! Definitely a lot of good things to think about. I’ve had the car for a good bit now and know that it’s structurally sound as is and would make a great daily. The biggest problem with getting a dedicated project is just not having the space or any good amount of money to put down on something. Then insurance and all that, you get the gist! Mainly with this I just wanted some way to sorta give the car a lil more spunk, ya know? Something small just to add a little bit of personality that is also fairly reversible. Again, thanks a million for your insight!

I totally get it! That was me for a long while. Watching all my friends with their cool cars didn't help either.

Nonetheless, I used the Bonneville to get through school. Spent more money than I should have trying various things from intake, ported manifolds, tunes, using 93 octane, you name it, with no real appreciative power gains. I even bought a turbo kit for it at one point and thankfully never installed it or the car would have been gone by now for sure.

It was really hard back then to make it through with the Bonneville sometimes, but I am thankful I did. I saved up my money, and when space allowed I got an S2000 and couldn't be happier with these two vehicles.

Highly recommend you do something similar, there will be time in the future to get a fun car. Don't waste your money turning this one into something it is not.

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-Car Guy Carl
"Penelope" - 2003 SLE - 247k Miles
"Sydney" - 2000 Honda S2000 - 98k miles

I second NOS4BLOOD70, but if you are dead set on the 3800 platform, your better off starting with a Grand Prix GTP (98-02) 2-door, they are lighter, supercharged, can probably be had cheap (knowing of course you will have to put a lot into it to make it fast and "reliable"), and in my opinion really the only contender for HP mods if you want to go fast...NOS is definitely right...performance mods on these cars especially N/A ones is like $1000 lipstick on a pig headed for slaughter. That said you can see in my signature block...I have done a few mods, but I would say it's only gained me the ability to get a speeding ticket easier.

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2003 Pontiac Bonneville SSEI
3.8L V6 SC, 180*T (Drilled),
Custom PCM w/Perf Shift,
SLP Ceramic Coated Headers,
Thrasher Cold Air Intake,
GXP Tails, Interior Door handles, Trim pieces etc.
40th Aniv Grand Prix GTP Wheels (Very Shiny & Very Annoying )

It's certainly an easier starting point if the car is already factory supercharged, but in the end you run into the same issues. That's not to say the car can't be fun, but I think going too crazy strays the car away from its intended design as a comfortable daily driver. It'll never be competitive either.

There is no one car does it all vehicle. You may not always be in the position to own 2 cars, but having 2 cars that specialize in different areas is always a better answer.

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-Car Guy Carl
"Penelope" - 2003 SLE - 247k Miles
"Sydney" - 2000 Honda S2000 - 98k miles

absolutely agree NOS, the mods I have make it easier to merge on highway/freeways, pass cars on 2-lane roads etc. and does make it a little more "spirited/fun" to drive. I actually have an inter-cooler I could put on, but haven't seen the need...if I do it wouldn't be to run small pulley and crazy boost, but to run a 3.4" pulley on 87 or 89 octane with no knock (looking more appealing as gas prices keep climbing). These cars are still a good daily driver performance and fuel mileage wise with a proper 3.4" pulley setup, but get beyond that I think the $$$ investment & Performance improvement VS loss of reliability/fuel economy for daily driving starts to skew in the wrong direction exponentially more so than the GTP cars due to it's size/weight and added stress on every component because of the size/weight increase. Most all the mods I have came from a "Junk Yard Find"....someone was crazy to leave it all on the vehicle: SLP headers, Siemens 65lb injectors, Thrasher Air box, DHP PCM, Ported lower intake, ported blower (stage 3 at least), Modular pulley system, XP cam (had to do some research to figure that out...just knew it was aftermarket when got it out). I bought the entire motor assembly just to get the parts....still need to rebuild/refresh the motor for a spare....just wish I had checked to see if the trans had any aftermarket goodies on it before they scrapped the car.

Sorry CDS, we kind of hijacked your thread here.

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2003 Pontiac Bonneville SSEI
3.8L V6 SC, 180*T (Drilled),
Custom PCM w/Perf Shift,
SLP Ceramic Coated Headers,
Thrasher Cold Air Intake,
GXP Tails, Interior Door handles, Trim pieces etc.
40th Aniv Grand Prix GTP Wheels (Very Shiny & Very Annoying )