Best mods under $500 are ???

[KLSuperCharged]

What gets the most horsepower for a mod?

I could tell a performance improvement when I replaced the stock muffler with a flow thru muffler.

Is it worth looking at getting rid of the camaro style muffler with one inlet and two outlets? Is it possible to go to a dual exhaust system?

I am looking at a high efficiency air filter system...is K&N the way to go?

Thanks.

[SuperSLE]

I would go pulley is the best mod for the money/HP gains. After that, rockers, cam, plog or headers, and PCM tune. Depends on how much work you want to/can do yourself. Cam would be the best with some exhaust mods. They aren't that expensive, just very labor intensive and require some other mods that add up.

[Allmachtige]

Depends on what you have already done.

FWI is $150ish, or $60-80 if you build it yourself.

3.5 MPS pulley system is $100

Shift Kit can range from $30 to $130 depending on who you buy from.

From there you choose between 1.9 roller rockers or a stage 1 cam. Cam ($300 + supporting mods) is for long term modification, 1.9's ($400 + supporting mods) are for quick and easy power.


....

However let's slow down. How many miles on the car? How many people have owned the car before you? What prior experience do you have with engines in general?

[00Beast]

Also, before making any more mods, make sure your car is properly tuned-up. It will not run to it's full potential with out it, and can possibly cause some issues, maybe even damage.

Make sure all items on this list are up-to-date, and you'll be good to mod for a while.

Brand Suggestions are in the parentheses.

• 1987-2005 Bonneville / Buick 3800 Maintenance List
  
  Run Seafoam through gasoline and intake every 5,000 miles. One pint of Seafoam in a half tank of fuel is a good mix. The intake is optional, but recommended.
  
  Grease: Ball Joints, Tie Rods Every 8-10k ( recommended) [b]Air Filter[/b] [i]Every 15k[/i] [s ... Amsoil EaA, Purolator PureONE)[/size]
  PCV Valve Every 30k
  MAF Sensor Element Cleaning/TB Cleaning Every 50k viewtopic.php?f=48&t=1661
  Fuel Filter Every 15-25k (Purolator, AC Delco, WIX)
  Spark Plugs Every 30-50k (NGK TR55 or Autolite 605) (Never Bosch)
  Ignition Wires Every 30-50k (Napa Belden, AC Delco, Autolite Pro, NGK) (Never Taylor or Bosch)
  Oil & Filter Every 5-6k or Every 6 months (Mobil1 or Amsoil)(Mobil1, Purolator PureONE, Amsoil EaO or WIX) (Never Fram) viewtopic.php?f=45&t=214
  *Conventional Oil Every 3k/3 months(Pennzoil with a WIX (Napa), Delco or Purolator filter)
  Transmission Flush Every 15-20k (Always make sure filter is changed when flushed)
  Cooling System Flush Every 25-50k or Annually (Peak or Prestone Green Coolant Only) (Never Dexcool)
  Oxygen Sensor Every 80-100k (30k for non-heated) (AC Delco or Denso) (Absolutely never Bosch) viewtopic.php?f=48&t=794
  Accessory Belt Inspect every 15k, replace every 100k, or as needed
  Cabin Air Filter Inspect and Replace every 15k, or as needed in dusty conditions. (Note: 00+ Only)
  Evap Core Cleaning Whenever Needed (Note: 99 and older only) viewtopic.php?f=45&t=2432
  
  *Special Considerations*
  All 3800s, LG3, LN3, L27, L36, L26, L67 & L32, especially important on vehicles factory installed with orange Havoline Dexcool Antifreeze/Coolant: http://www.dex-cool.net/
  Lower Intake Manifold Gasket Replacement, every 80-100k (ignorance of this can allow coolant to enter your engine oil, this happening can cause irreversible lower engine damage, requiring replacement of subject engine)
  
  Series II, Naturally Aspirated, RPO:L36:
  Upper Intake Manifold Plenum Replacement, Every 80-100k (ignorance of this can allow coolant to enter your intake manifold, possible damage to occur can be hydrolock, irreversible damage to emissions devices, misfires, etc. Most times, engine replacement is required if ignored long enough.) viewtopic.php?f=53&t=1061
  
  Series I, II, III RPO Code L67 & L32:
  Change Supercharger Oil; Every 30-50k. (Intense Racing or GM Dealer) viewtopic.php?f=56&t=1690
  Supercharger Belt (Series II and III only); Inspect Every 15k, Replace Every 100k or as needed.
  
  Rev. 6/7/09 By 00Beast