(2001 Bonneville SSEi). A few days ago my "Service Engine Soon" light came on and yesterday when accelerating hard to enter the freeway, I noticed immediately noticed it running rough, with vibration in the wheel when accelerating. Until that hard acceleration it had been running great and I had already been on highway for 2 hours. I am currently having trouble with my EGR in the truck so immediately thought it could be that in the car, but I am usually never lucky when it comes to the Bonneville. When coasting it was fine, but today it runs a little rough just idling in the driveway. All fluids are fine, all gauges read fine and it's giving me no code. When I checked under the hood the engine seemed to have quite a bit more movement in it then usual. Thought it may be a mount but the front looks fine. The service engine soon light was on months ago as well and I replaced the gas cap and it went off. Hoping it's something fairly simple but with the luck I have had with this car, I know it won't be. Seems this little "biotch" needs constant pampering. I'm almost afraid to step on the gas anymore for fear something breaks. :( Going to change plugs and wires tomorrow, it's been a looong time since they were done, hopefully that's all there is to it.
Thanks in advance for any help you can offer.

The SES light flashing indicates a potentially catalyst damaging condition. It is most often caused by a misfire. Your boost gauge should not be anywhere near zero at idle. Start by looking for vacuum leaks paying close attention to the "T" fitting from the LIM under the supercharger snout, and the associated lines.

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*Gone, but not forgotten* - Black 2000 SSEi, HIR Headlights, Angel Eyes fogs, 3rd brake light overlay, hi-flo cat, 180 degree thermostat, HS 1.9 rockers, LSx yellow springs, Intense FWI, PCM, shift kit, push rods, and 3.4 Pulley. ZZP Power Log.

Sorry, I had a brain fart, it's slightly higher than -70 Kpa, sitting half way between -70 and -35kpa (next indicator line for boost) approx. It is not near the zero at all, I apologize.

Part Source put the code reader on it for me and P0204 Injector Circuit Open code came up so I guess my Cylinder 4 injector is screwed. We tried cleaning it and it runs better but still not right. Anyone know where I can get Rebuilt INjectors in Ontario Canada? Found one for $30 USD but can't find the link again. Might as well get a set for those prices since we will have it apart anyway? Any thoughts? Anything I should know when changing them all out as a set? Thanks again for the help.