There have been postings in past by people that have had a problem with the flexible air intake dust (from air box to throttle body) wanting to collapse under heavy throttle. This is hard to simulte though simply by reving the car in neutral. You may see it if you have an assistant put the car in gear, hold the brake, and then throttle down. If you do this be sure to observe from BESIDE the car vs in front. I would have to think that if the duct is collapsing you would surely want to explore for an air box restriction as James suggests - deteriorating foam, super dirty filter element, airbox full of dry dog food, dead animals, etc., in addition to just replacing the duct.

A restricted exhaust system can also cause these symptoms - clogged cat or muffler. If you still have the original cat the honeycomb may be breaking down and clogging the exit.

BTW - code 3-2-1 is to be expected if your car received the post-production cold start mod which, as being a 1990 Regina, it should have. Ignore that code.