The V6 runs fine at all speeds. Tranny shifts without issue. The strange thing is a light smoke rises from the engine block just as the engine warms up. Engine starts with its high idle then when warm idles down to its normal speed. Two things I've investgated. Investegated a minor leak in the brake reservoir dripping on the manifold (the car sometimes is low on brake fluid); or did I lose a seal in the engine block that I've heard is a common problem with the 93 V6. This is a car that I do not know its history. My expertise is the 46 to 53 Chevy Stovebolt six/Rochester single barrel with poured babbet bearings. At least the stovebolt you could work on.....lol.
Light gray smoke comming from engine compartment on 1993 Pontiac Bonneville
if you are only getting light smoke from under hood. and youknow you are getting brake fluid drippoing on the manifold it is probably the cause of your smoke as it burns off from engine heat it will smoke. Is the smoke coming from that side of the engine? Repair the brake leak as needed and see if the smoke goes away.
if it leaking brake fliud on manifold that will make it smoke if u need help call 9106545823