I understand that pollution controls sapped the engines of their power. I still believe, however, that the engineers could have done something in their powers to tweak at least a modest 150 h. p out of the 4.1 or the other engines. That would not have made them lightning quick, but at least people would not be scared of merging onto a busy highway. But then again I'm no mechanic so who knows.
Well, engineering takes time and money, neither of which the American car manufacturers had when the new pollution controls came into effect during the 1970's. So they took the easiest and cheapest route. Also remember that this was the beginning of the Roger Smith era, which set GM on its course to failure that is still happening today.
General comment to all 1981 Cadillac owners:
The V8-6-4 engine is a rarity, and a lot of mechanics aren't familiar with it (unless you take it to a GM garage with older mechanics). Go to ebay and search on 1981 Cadillac. Odds are you'll find the original GM Service/Repair manual - there seem to be lots out there. I purchased mine for less than $20.00 US! Tons of valuable information on this engine and how to keep it running, plus easy to follow trouble shooting trees.
To give an example, when I bought my car, the battery was dying every time the car was parked. The dealer I bought it from tried everything to find the problem and couldn't. GM found it in 20 minutes - it was one of the variable displacement solenoids. The solution was to simply unplug it and leave the car running as an 8 cyl. I may replace the solenoid on my own time, but it's running fine as an 8.
I have the same car, with the same problem as yours. Where is the plug for this solenoid, can you please post any picture of it, I would really appreciate it. Thanks.