I have been working on getting some things done with my 2000 GTP (wheel bearing, sway bar, etc) and it has been "out of commission" for 2 days while I've been working on it. My fixes/mods have been going well, but I installed a ZZP stainless steel PLOG yesterday, but didn't drive the car until today and now, all of a sudden, I get studdering under boost. Light studdering under low boost, and not a ton under WOT, but very noticeable at about 50% boost. This doesn't matter if I am going 25mph or 65mph.

The PLOG is the only engine upgrade I've done in several days, and I don't recall ANY studdering prior to it going in place.

Earlier this week I put on my TDC FWI and drove the car for 3 days without issue before starting this current batch of repairs/mods.

I don't get any SES light at all, not even a flicker. I pulled into the garage after my test drive and without load, I can hit the throttle pretty good without anything negative happening. Of course, the supercharger doesn't seem to be "engaged" when I am in park/neutral, so if it is a boost issue, that would make sense. Of course with no load, it isn't really a great test either.

A couple of weeks ago I upgraded to a 3" catted downpipe. My goal was to let the car breath and remove any * KR. I wasn't noticing anything, but I am just trying to get ready for a pulley drop later this year.

Other details related to the engine are as follows:

Vehicle has 55,400 miles (yeah, that isn't a typo).

Oil change/filter completed 6 weeks ago.

Spark plug wires were replaced a year ago as my one coal pack had a little rust that trashed a wire. Coil pack is still original, but rust was removed from it.

New battery was installed 4 weeks ago (I know, probably not the issue, but just being thorough.)

Coolant was flushed 4 weeks back.

"Dog Bone Flip" done 4 weeks ago.

180* T-Stat put in with the coolant flush.

3" catted downpipe installed 3 weeks ago.

TDC FWI installed 6 days ago.

PLOG installed yesterday (plug wires disconnected to allow for removal, and they were reseated after PLOG was in place).

Like I said, I didn't notice anything performing poorly until my first drive after the PLOG install.

Last item of note. I am still researching this as I simply don't know, but after we had the front 3 plug wires removed to get ready for the PLOG install, we changed our plans and started tackling my broken sway bar. At one point my dad, bless him for being here to help, started the car for about 2 full seconds with only 3 plug wires (the rears) connected so that he could use the power steering to turn the wheels for better access to things under the car. I hope that didn't screw anything up.

So any thoughts or ideas would be helpful. Again, there is nobody anywhere near me that is able to do a scan, which makes things tricky.

Thanks everyone.