Stock '89 to '93 SC's came with 30# injectors. If your car has an SC engine and electronics in it, and it's running 19# injectors, you're going to have problems.
Enough guys around here have upgraded their injectors that you should be able to pic up a used set of 30# injectors easily enough. I've got a couple spare sets myself. If you go the route of buying used injectors though, I would suggest you look at having them professionally cleaned and flow tested before you install them. There's a place in Toronto that did a set for someone I know, and it cost around $25 per injector.
Good luck!
Sean