I'm a newbie here and in need of some advice. I'm at wits end. I have a '94 K1500 that I've had since '97 and have done all the work on her that she ever needed. (So far.) Over the past few days it began so "slow down." I mean I needed to give it more throttle to get up to speed. I noticed the throttle body giving the "throaty sound" just coming up to cruising speed on the freeway. Then it happened. Full throttle gets me 50mph on a good day. It was time for a tune up so I threw the norm: Plugs, Wires, Cap , Rotor, and PCV. All Delco parts. She'll idle but as soon as those butterflies open it wants to misfire. I had an issue with the TPS before so I bought one just for kicks. (AC as well.) No luck. So far I've checked temperatures on exhaust manifolds as well as the cat to see if it's plugged. Temps looks normal. It appears to have enough fuel but I haven't yet put a gauge to the pump. Does anybody have any ideas to throw in the mix? What's confusing is that it idles smooth. Doesn't shake, doesn't miss, just smooth. I'm lost. Any help would be appreciated.