The Howell system “tune” is very similar to a stock GM tune.
They changed VERY little.
The fuel map is ok-ish for a stock cam.
When a larger cam is used, and vacuum decreases, the whole map is now way off. The fuel map is based on RPM vs. MAP(vacuum), a big cam & lumpy idle it will bounce around on different cells of fuel map.
The fuel map needs to be correct before changing things like acceleration enrichment.
Even a stock engine/cam benefits from a tune. Regardless of what people say there is no such thing as a turn key system. The ecm can only “learn” & adjust so much. If you have a bad tune it’ll never run “right”.
If you want it to run better/correctly you gotta tune these.
'88 GW (aka Babywag) and '90 GW (aka JUNKbucket) both fuel injected
1994 Caprice wagon