air/fuel mixture

[zdude]

i think the previous owner f'd up my a/f mixture, maybe to "give it more power" which isnt gonna happen considering he knew jack sh*t about cars... anyway, when ever i accelerate, it back fires between shifts, sounds kind of cool when im really on it, but normal acceleration it sounds like a$$. also, when its idling, it sort of pops every couple of seconds, i heard on a different forum that that is normal, but i was wondering if that could be solved with the renewed mixture...also, i havent messed around with this sort of thing yet, and neither have any of my friends, so i was wondering how i would fix the a/f mixture...my first idea was cam timing, but now that i think about it more my guess is the valve timing

thanks
paul