I missed that, and was responding to a post 89 where he said he would check the cap. Oh well.
I see he said he also replaced the plugs as well as most all of the ignition system. Thought I'd mention that when I got my plugs recently(Advance Auto) he strongly recommended the expensive($6+) Delco Platinum plugs gapped @ 0.060". I asked to get a cheaper Bosch plug when the guy asked another person behind the counter "what plug do you need for a late model Chevy". The other person didn't hesitate and replied the Platimum plugs. The guy I was talking to then asked the other "why", and the other's reply was that the other plugs were too cold and would cause misfiring, the same the guy I was talking to had told me just before. I bought the platinums. Just thought I'd mention that.
I noticed the OP's pics of the plugs, and with the one exception they seem to be extremely light in color as if almost too lean a mixture. I know that a lean mixture is harder to light than a rich one(especially under a load) and since he has already replaced most of the ignition(I hope he got the right plugs), I'm with those that suspect the fuel system.
I don't think he has the same injection system I had. I had the "Central" injection system with the "poppets" at the ports instead of individual injectors at the ports(MPI). If he has the poppets I'd replace them without hesitation for the retrofit conversion kit with MPI as I did.
If he has the individual injectors at the ports I'd remove them, and take them to a shop, and have them professionally cleaned. At approximately $40 a piece new its worth a try to save them by cleaning IMO.
PS Before you do anything, try what I suggested on post 74 about listening for a leak with a piece of hose. Only cost $1. A leak can make it lean. Might think that a leak would make the MAP sensor read low(under load) and richen the mix, but not necessarily.
Last edited by ssmonty; 03-24-2013 at 12:53 PM.