i have a 91 z 28 350 that surges only at crusing speeds dosent matter what speed, it can be at 50 kmh to 100 kmh and it still surges, with my foot to the floor it seems to run fine. i first sespected timing i checked the timing rotor and cap all three were good, new plugs and wires were just rescently done, double checked the the plug wire order and still surges your advice is greatly appreciated thanks

try your fuel filter and if it is an aftermarket pump then that might be it as well