The 'roughness' is pretty much only noticeable at idle, the car runs great at high revs. Still dynoed at 290rwhp despite whatever this issue is.
I'm definately going to try this, but like you said if the car runs well at high RPM's it's doubtful
The plugs all look the same, I swapped plugs and then installed new ones to assure that wasn't the problem- and it wasn't. The #1 plug still looks like all the rest. I also swapped the wire with an extra set I had and it also didn't help.
Is this hard to do? I will give it a shot, although my opti is fairly new. Could a corroded signal cable cause problems in only one cylinder?
I sent my injectors off to be flow tested and cleaned, and when they got back put them on in no particular order and the engine ran exactly the same.
The "cold" cylinder is at least 100 degrees apart, I haven't tested temps at high throttle but when I park the car after running it hard the #1 cylinder can be touched while the rest would melt my skin off.
Nope.
Nope.
The radiator seems fine(I dont know how you test it for pressure but I don't have any coolant system issues). The MAP reading is within spec so I don't believe I have any vacuum leaks.
Yup, cleaned everything and made sure it was all moving freely

If the problem is not internal then it might be ignition related, even though I am getting spark? I ask because when I had my opti changed there was a 4 prong cable that had corroded connectors that the GM tech(I was on the road else I would have changed it myself) couldn't replace. He ended up cleaning them up and replacing the prongs, but if the cable is bad could it cause issues in just one cylinder? Even though the rest get hot, and all have spark? I might be barking up the wrong tree but with all my troubleshooting, the cold header is the only clue I have to my rough idle.(and it's not terrible, just random slight misfire sensations that bug the hell out of me)

 

Looks like you checked everything but what about this. Supposing it is spark related, it's highly unlikely its related to the optical portion of the opti. Usually problems with the opti are with the high voltage "distributor" portion. Because of the "correct-a-cap" design, the high voltage leads going to the contacts are very close to each other. Causing breakdown and carbon tracking problems. I saw above where someone said to pull the cap and you replied you would, did you?

If you had an intermittent spark signal going to a plug, perhaps an inductive timing light would show a different "light flashing" pattern than the other cylinders. If you let it idle and connect the timing light to the suspect cylinder and compare it to others.

Easy way to see.

Dave

 

Can you be a little more specific about the temp of the #1 cylinder after it has been run hard??? Are you refering to the cylinder head itself of the exhaust manifold/header tube??? If you are refering to the cylinder head, what part are you actually touching??? I wouldn't be too concerned about temp differences at an idle as I said earlier, but I would definately look further at a cylinder that is noticably cooler than the rest after actually driving the vehicle. As Slopok stated above, the secondary wiring for that cylinder ie. plug, ignition wire and most of all cap/rotor need to be looked at very closely. Also as Slopok mentioned, using a timing light to compare spark patterns between the suspected "bad" cylinder and a "good" cylinder may help to verify a secondary spark problem. Let us know what you find. Good luck!