Need Help My1994 Blazer Has Miss

[ss4OU]

I have a 1994 Blazer with the 5.7 and 208K. It has a miss/back fire that comes and goes. It will usally happen between 2K and 3K. If I am on the highway I can take it out of over drive and sometimes it will be OK but when I start up a hill it will start to miss again usally clears up above 33k or so . It does not happen every time I drive it but is starting to do it more often now and when it does act up is running worse. The check eng light does not come on when it happens. It is not bad gas. Truck has only quit once. usally doesn't happen at slower speeds. More so under load at maybe 40 to 65 mph. But like I said it does not happen all the time. It can act up, then next time I drive it no problems. The truck was well taken car of before I got it and I have only put about 8K on it in the last 5 years so it isn't driven much. The shop doesn't know where to start without just blindly replacing things at my expense. Any ideas? cap, wires, fuel filter, O2 sen? Thanks everbody here seems to have some great ideas