2002 Lincoln LS V6 1st Gen. So today after work my car spit a 2 codes P0304 and p0174 pending... Hooked up to reader and saw misfire cylinder 4 and a bank is running to lean... Just recently did all coils, sparkplugs, egr valve, intake manifold gaskets, cleaned throttlebody, did alternator cause battery wouldnt keep charge. Took out MAF cleaned aswell. Also changed the PCV Valve and the rubber elbow. Had no problems or engine lights for 2-3 weeks and now I have this problem.. My defrost makes a burning rubber smell now aswell which im almost 98% sure is the compressor.. but im stumped on what is throwing me these codes.. Car revs from 1000-2000 sometimes until warm and stays at 2k if i give it gas once for about 5 secs.. I'm almost 90% sure this is the iac but i dont want to go waste money.. Now i've read some posts about the Manifold "O" rings being out of placement and go back into placement once the car is warm.. Once i start it for the day its pretty good unless it gets decently cold out.. My guess is Iac is stuck open.. Any advice ?