I have a 2001 silverado with a 4.8L V8 with 222,000 miles on it. the truck ran fine with no major problems then one day i let someone use it and they drove the hell out of it witht he ac full blast and almost over heated it (the temp gauge was past 3/4). one week after that I got the p0171 & p0174 check engine codes. it says it something with the fuel system or the o2 sensors. I replaced the fuel pressure regulator. my fuel pump is fine (58 psi), my o2 sensors are ok, i replaced the MAF sensor, the fuel injectors are good, i replaced the fuel filter, and i have used any fuel cleaners or additives in my tank. I dont know what the heck is going on. the codes pop up when the engine is dead cold and when i start it and theres a ticking noise coming from the engine that sounds like a rattlesnake tail. the ticking noise gets louder and louder as i step on the gas but quiets down when at idle. ive checked for a vacuum leak but didnt find any. ive read online that it could be the intake manifold gaskets but it rarely happens. could the almost over heating of my truck have caused the gaskets to melt or break? any advice or help is greatly apreciated cause this truck is my daily driver and this problem has been affecting my mpg a lot. thanx in advanced. oh 1 more thing. are all 99-07 chevy fullsize truck intake manifolds interchangable? im thinkin just to buy a used low mileage manifold complete with injectors, rails, and throttlebody. I know that after 2005 gm started the gen 4 engines but the intake manifolds look similar? anyone thats knows this would also help me alot thanx.