94 G STANG

Guys I know its not a stang but I trust the knowledge on this site, got this e250 van in for a bad idle, its runs rough almost like it coughs and causes a stumble at idle. Koeo no problems found, same with koer. I did the plugs wires cap rotor coil iac valve. The sensor values are normal and I put a new o2 sensor, I installed a spark tester and the sparks seems ok then kinda fades and gets better again. I tried replacing the dist to no avail, fuel pressure is at 35 and 40 line disconnected with new fuel filter. The only thing that seems funny is the vref on the codes menu of the scanner is 6.68-6.71. Bad ground? any Ideas guys no vac leaks as I sprayed all around the inkate and no idle difference. 5 gas analyser shows 0.5 co with 30ppm hc and rises when it misses so I believe its getting sufficient fuel.
Let me know guys if you ran into anything like this or anything I overlooked?

tommiesgt

we got a 94 350 at work with the 351 in it had same problem, did tune up didnt help, it would stall once in a while too. Ended up being the coil. it was like 20 bucks, just a thought?