but would running the hotter cap and coil setup from the ford equal that out
However, if you're stumbling because you're running rich, that means your fuel metering and feedback are probably off. Check/replace MAP, IAT, and HEGO sensors. (The MAP and IAT are standard GM parts - if you can't find them anywhere else, Marren Fuel Injection has reasonable prices. Google them. The HEGO is an oddball, but it's still available at/through your local - Bosch has a part number that works, but I don't recall what it is. Bosch is OEM for most anyhow.)
If fuel trim is causing you to run silly, then fix your fuel trim. Hotter ignition is like treating a broken leg with aspirin - it will mask the symptom, but it doesn't fix the problem.
Also, use an analogue ohmmeter to check TPS sweep and function - they're known for developing flat spots in the track (due to the way they're built. It does take some time...) and the fix for that is replacement. Using a digital ohmmeter will not
give an accurate test, you must
use an analogue for the check to mean anything! The test takes about two minutes - you're just making sure that the sweep of the sensor will not "skip" or "stick" anywhere on the track. That usually happens at the part-throttle opening that corresponds to where you cruise the most.
Going from 18-19# to 21# (at the same pressure delivery - I think early HO is rated for the same pressure as RENIX...) should not cause signficant fuel trim problems - the system can adapt for that (I have 21#/hour in my 88, and no trouble there.) However, switching to the larger injector can bring a problem elsewhere to light - and that may be what happened for you.