You're pretty much right on it. also check the pipe just below the exhaust manifold. that had a leak the same time my intake had a leak. caused stuttering and shaking. also check and make sure your ignition module is functioning alright. check your plug holes for oil and your plugs for carbon or oil deposits. O2s can cause bad mileage. I'm at about 19-21 mpg (this is above normal actually) I know i need to change my PCV and prolly my O2 sensor. good luck.HuD_91gt said:Hmm just occured to me, could it be a leak off the Vacuum hose that comes off the silencer right after the VAF?
Also, my car blow some oil, and I am getting bad mileage(~20mpg), could a fouled O2 sensor cause the bad mileage, where is it located?