When would start the car cold, it would sputter and occasionally die. It started right back up and ran fine until one day it wouldn't start back up again. We finally got it started, but couldn't keep it running. We had plugs, cap, etc. replaced and now it runs(sounds ok), but there is a loss of power. When stepping on the accelorator, it won't get over about 35mph. The car is a 1986 Pontiac 6000 SE (6cyl).

Optional Information:
1986 Pontiac 6000 SE 6 cyl

Already Tried:
minor tune up consisting of replacing plugs & cap, checked plug wires. The fuel does seem to be coming through to engine.