inconsistant rpms and bogged down after driving

for first minute of the day but always sounds good at an idle. Where do I look for the problem?does not overheat, but bogs down and recently I'm smelling gas fumes. It especially bogs down but when I put a load on it. (20-30 mph max. Check maintenance light is also on. Recent repair about 6 mos. ago for a similar problem. I think they replaced 8 intake gaskets of some sought.
Engine is a Northstar V8 32 valve.