is there any negative effects or reason SWIM should not smoke a cigarette after smoking changa?

Other than the fact cigarette smoke is detrimental to your health in the long run, they are not contraindicated with harmala alkaloids.

alright, much appreciated

Could smoking cigs on an MAOI increase the effect of the nicotine?

I doubt it.

Nicotiana rustica contains harmine tetrahydroharmine and harmaline, as well as nicotine, I don't notice a nicotine potentiation when I smoke it, kind of the complete opposite.

Your mileage may vary.

yes for sure it does...with mapacho and caapi anyway.