i got a small header gasket leak and i cut the valve off the driver side air fitting (only one bolt for pass side) but i just crimped it closed as best as possible. my gas miliage is worse than ever and i smell gassy exhaust when idleing or coming up to a stop

 

Yes... the leak inducts air into the exhaust, the O2 sensor "sees" the air and indicates lean, and the PCM adds more fuel, that you don't really need.

 

ok
thats what i thought. what if the gasket leak is small like not really loud

i can fix the air pipe off the header but the gasket is new and tight as hell so dont know if i can seal it. i might have to double up the gaskets and make it two gaskets instead of one. i dont know if its a cracked header or bent flange or what

 

what about a leak at the drivers side collector on a 97 ??? we had to drop the pipe and cat on that side to get the lt4 starter in , less than a week after we did that the drivers side bank started adding about 30% of fuel when cold slowly going back to normal the warmer it got it seemed. on the other hand the other bank is leaning itself out for some reason.