I have a 96 Chevy k2500, so was at the store, going to the store, everything was fine, got out of the store, started the truck up fine, but i could tell right away the idle was rough. Felt like it was running on 6 cylinders, backed out and started to drive and could tell it wasn't running right. Headed home, and when it was on just cruising down the road at steady 45, was smooth, then going up a hill, i had to gun it, and it was not sputtering as much as just running even more rough, then i heard popping every few seconds, assuming this was backfire. Got it home, turned it off, starts up without any issues what so ever. Tried a few times and starts up just fine, but rev'd it up and still sputters/rough rev, and no smoke what so ever, any input?