It may have been rebuilt, but maybe they just re-did the longblock and kept all of the old equipment without freshening them up as well. My buddy had an '81 Chevy pickup with a 305 that he had a shop exchange the motor for a rebuilt one after 200K miles and all they did was give him a fresh longblock and transferred all the old stuff over without giving it a tune-up, therefore after a couple of weeks it was running like crap. Tell your friend to give it a complete tune-up=ignition module, coil, cap, etc.; clean the TBI or carb with some carb. cleaner, and change the air and fuel filters. The feedback, electronic carb., if equipped, are notorious for running crappy no matter what you do to them after some high mileage, so your buddy may have to fork over some loot to get a fresh one. Don't even bother going to a junkyard for one of those carbs. because you'll just end up with the same crap all over.