2000 GTP Idles rough

I have a 2000 GTP that idles rough. It sounds like a misfire. When I rev the engine (in park) upto 4k RPM's, the RPM's & idle will start to bounce! I have already changed the plugs, but I am unsure where to look next. Any Suggestions?

stop doing that, your hitting the rev limiter, it will do this in neutral and park.

What plugs and what gap?

And yes the 4k is your rev limiter, so stop that.

Maybe you should research more on your problem, you'd find cleaning the throttle body and MAF sensor can be very helpful.

2 things.

Our cars, especially modded do tend to misfire at idle. Though enough to cause it to idle rough sounds like something more.

2nd, if the car is misfiring, your check engine light will flash on and off.

What plugs did you put in, and what did you gap them to? Are there any mods done to the car?

How old are the plug wires? Did you make sure that they were all contacted with the plugs well?

Does the car run okay driving, or does it misfire while driving too?

IIRC the SES light only flashes to show Multiple misses..

Do you still have the screen in the TB? Also have you made any changes to the intake?

Plugs are Autolite Double Platinum Spark Plugs, Gapped to .06! I have just taken it to the local Adavance auto parts to run the code. Misfire in #4, Also something w/ the catalyst which could also be caused by the misfire (per the guy that checked the code). going to look into that tomorrow morning. Thanks for the info on the Rev Limiter, didn't know there was one equipped on the car, clearly I'm an amatuer at best!

ditch the double plats, these cars dont like them, get some nice iridium plugs, or copper core plugs.

that will fix your misfire most likely. gap the new plugs at 55

^ This exactly.

If that doesn't cure the hiccup, get some MAF cleaner and clean the MAF.

Stock AC delco plugs are what you want.

Turns out it was the Coil pack for 1 & 4 Cylinders that was causing the misfire.