I have been having trouble with my 86 Z28 with a 305. It will run very well thru 1st gear once you hit 2nd it cuts out. Like it is running out of fuel or something. I have replaced the carb, plugs coil unpluged the computer adv and bumped up the timing trying to stay ahead of the curve, fuel filter and it has a new fuel pump. You can hold it a 4 grand all day unloaded but with the car in drive same problem. Can anyone think of something, I was thinking of pulling the gas tank out to see if the pick-up was cloged, waiting to get the gas tank lower on fuel.

 

Lean?

Weak spark?

Exhaust restriction?