Hi guys I seem to be having a problem with my 89 F150 4.9 stumbling at lower rpms. I recently have put on brand new plugs, wires, TPS, IAC, Fuel Pressure Regulator, Fuel Filter, EGR Valve, EVP, and EGR Vacuum Solenoid. I was recently getting a code 33 about the EGR being stuck, so I cleared that by putting on all the new EGR parts. Ever since then my truck seems to have lost a lot of power, and it stumbles at lower rpms, usually in 1st and 2nd gear.

The exhaust also makes a funny popping noise that it hadn't done before while sitting at idle. I did get a code 41 the other day which I believe had to do with engine running lean. I put the new pressure regulator on and cleared the memory and the code didn't come back up but it still runs crappy. The only other thing I have noticed since I had the truck is that the temperature gauge never goes above the beginning of the cool line on the left side of the gauge, and never once has gotten to the middle of the gauge near the normal temperature. Even after long trips it still is cooler then I think it should be. Could this problem I am having be related to the Coolant Temp Sensor, blocked exhaust, 02 sensor, or maybe even the fuel pump? I really am sick of buying parts to fix this problem, and I even had it looked at in the shop with no positive results.