starting up issue and studering while driving issue

the problem I am having with my 99 galant is that it will start studering while driving down the road, but if I let off on the gas and reapply the it will run normal for a min or so then back to studering. it only does it after being drivin for 25-30 mins. then last week drove it to the store 5 min. down the road. when I came back out it didn't crank right up like it always does, turns over but doesn't start right up. took me 5-6 tries before it finally started up. tried it a few time when I got home. sometime after 2-3 time it will fire up on the first turn over on the next try other time it will fire up as i'm letting the key go. this only happens after the car warms up to normal operating temp. but first start up of the day it will fire right up. so what I've done so far to the car since I've had it, had to replace the cat. convertor when first got the car, then replace the plugs and coil packs to try and fix the studering while driving down the road. didn't fix it. so now I have replace the crank sensor, fuel regulator, and all the injector. none of these have fix either of the problems I am having. after replacing the regulator and injector, it seems to help. don't have to try as many times when car is warmed up. 2 maybe 3 at the most. but car still studer while driving, just not as violate as before. the only thing I can think off is that it's either the relay or the fuel pump. is one of these 2 the problem or could it be something else?

Based on what you're saying and all of the parts you've already thrown at the car I'd have to go with the fuel pump going. Only real way to know for sure though would be to check the line pressure to see if it's in spec. Check engine light on or no?