I'm not familiar with your exact regulator, but I can tell you that a faulty regulator can cause multiple symptoms, some more prevolent than others.

Also- a warm engine is more tolerant of fuel mixtures being overly lean/rich than a cold one. The older impco regulators had no provisions for cold fuel enrichment. If the electric "trim" device you speak of is malfunctioning, do yourself a favor & replace the entire regulator (with the fuel trim solnoid) attatched- you'll save alot of frustration in the long run.