The "O" rings are a possibility Phil, use some silicone grease (not sealant) on them to help them "find" their pressure-tight position and slip in easier.
Have you checked the Throttle Position Switch to make sure the idle switch is operating? Sometimes called "Throttle Closed" switch as well.
Also - B200F - i know it's a 1990 car and therefore too early to have a mandatory cat but does it have a cat and Lambda sensor? If so, it's possible the Lambda could do with renewal.
However, if the lumpy idle is present from cold, ignore those two ideas. They will only be relevant on a hot engine.
If it's present from cold, have you checked the large diameter hose between the throttle body and MAFF? Even a pinhole in this can cause problems!
I think you may need to renew the dizzy cap and rotor arm though, it sounds compromised and if so, even after cleaning, it will still be compromised.
