I've got an 85 stock K30 with a 350/SM465 that has a bit of a backfiring problem. Typically, this occurs when I'm trying to get speed up quickly. My plan is to give it a tune-up when $$ allows. I plan to change plugs/wires/cap/rotor/fuel filter/air filter. I've alos tried running fuel additive to try & clean out system but it still does it. Anybody know what the source of this problem might be? Any comments on my tune-up? Anything else you'd change as well? Thanks.