'97 Sunfire Stalling on accel (w/ fault codes)

[LanceS4803]

I have a new to me '97 Pontiac Sunfire 2.2l with 130,000 miles.
Starts great, runs good, but wants to hesitate and stall on acceleration or braking.
I have replaced fuel filter and regulator. Fuel pump checks out fine, have had injectors pulled and cleaned. New plugs also, didn't detect any evidence of problems with condition of old plugs.

Took to GM dealer and it shows fault codes of:
P0300-Engine Misfire Detected
P0172-Fuel Trim System Rich
The technician said someone installed two different brands of injectors and "believes" these are causing the hesitation/stalling. He said it is no guarantee that new injectors, at $176 each, will fix the problem.

Will a new set of injectors fix this?
Any problem with using non-OEM injectors or rebuilt injectors?
Any other suggestions?
Other than this, the car is a great vehicle. Any advice much appreciated,
Lance