Help with fuel injection issue

I've been trying to diagnose and fix my 99 jeep cherokee. She fires right up when cold, but once she gets warmed up it is harder for it to fire up. Since my fuel sending unit was acting up, I replaced that whole set up, but the issue is still there. I started looking for a vacuum leak and didn't find one, so I replaced the purge solenoid, but again the issue is still there. I keep getting random fuel loss surges, rough start up, and slight hesitation when driving from a stop. Although my engine runs a whole lot smoother now. No check engine codes have popped up, and all of the relays and fuses seem to fine. I'm coming up short handed all around, and have came to the conclusion that maybe it is time to start replacing the fuel injectors.
Please any help and suggestions would be greatly appreciated.