Boy, does my son's slant run crappy!

First grab the carb and try to wiggle it. It may be lifting with the throttle if its loose. Start it , let it run to warm and verify choke fully open. Cup your hands down over the air horn. Just an easy way to check for vacuum leaks.
If the engine dies ( smothers it ), cool. If the rpm picks up you have a mixture problem. Visualy inspect evey vacuum hose, pcv valve, egr valve.
Hurry back :)