Just to echo @db4690, I had to replace the intake gaskets on my Ford Explorer to solve a recurring lean burn code. The gaskets I pulled out looked good, but replacing ythem eliminated the problem.
On my Supra, I had to pull the plenum to get to the plugs and the gasket kit they gave me was wrong. Put it back together with the old gasket, and it started hunting for idle, a classic vacuum leak symptom. Got the right kit, installed the gasket, and idle returned to normal. Both kits were inexpensive Felpro, and worth every penny.
As a matter of fact, I also used a Felpro plenum gasket. I actually bought the gasket kit. It also contained a throttle body gasket, which I didn’t use, because I didn’t separate the throttle body from the plenum.
Naturally, I cleaned the throttle body while I was in there.
I rather like Felpro. I routinely use them for intake gaskets, cam seals, crank seals, etc. I believe they’re high quality, and the parts stores usually stock them. I have noticed that Felpro doesn’t always correctly duplicate water pump seals, especially the rubber impregnated metal seals.
ah yes, I remember when I used to enjoy working on my vehicles. even tho the OP seems a bit thick headed about gapping the plugs, its nice to see his enthusiasm and curiousity
ok i replaced the gas cap, now the P1450 code is gone, P0456 code remains after a fewdays.
The main problem is I’m not getting any mileage improvement, if any I’m seeing slightly worse mpg, even though the car runs smoother and seem to have more power… is that normal? do I need to re-do the job with new gasket even though I’m not getting any lean code? P0456 is the only code right now.