What would make my 1990 Corolla witha 4afe start serging after putting in a bottle of injector cleaner

It may have caused dirt to loosten and that may have caused an injector problem. If the engine idle is going up and down, check the IAC. Also, you may want to run the vehicle a while longer (as long as it isn't unsafe) to see if it cleans itself out. There may just be dirt making its way through the system.