Anybody have this trouble with this engine? I'm hoping its a bad plug or wire. Are those heat shields/tubes around the #3 and #4 plugs supposed to come off? They look pretty rusted to the block. I sprayed some wd-40 on them and tried and tried but i just could not get it off. The plugs look like they havent been changed since the truck was new as evidenced by big gaps. Would a tuneup really fix the problem? I had the code checked at autozone (which i HATE to do) and it came up P0303. Just wondering what the possible causes are. Thanks all.

Just to clarify, I was able to pull #1 and #2 plugs and look at them....

 

Had a tuneup and now #8 cylinder is showing misfire (P0308). Filled it up with new, high-octane gas and tightened down the #8 plug wire (which the tuneup mechanic left loose) and problem seems to have gone away. Appt. with dealer in the morning, will update you all then.

 

Along with the tuneup, I would clean the IAC, throttle body, and MAS. Be careful when cleaning the MAS as it has tiny wires that can wreak havoc when messed up.

 

Ends up being a cracked #1 spark plug. Tuneup place messed up the installation and cracked the white ceramic part (porcelain?). Dealer replaced and problem is completely gone. She runs smoothly yet again. IAC, Throttle body and MAS are always clean, I clean them all when I do my oil changes. Thanks cobra for responding.