A firearm is a system. The bolt group needs enough energy to cycle. Too much energy in the bolt group makes for excessive recoil at a minimum. Too little energy in the bolt group and the mechanism short strokes. "Haris1", what I got from your OP is that you increase the mass of the bolt group by using a heavier buffer and you added a stronger recoil spring and now your 9mm AR doesn't want to run. I have found with 9mm blowback that a lighter recoil spring tends to make the mechanism run more smoothly. A heavier spring tends to drive the bolt group back into battery with more force.
One of the best combinations of springs and buffers seems to be the 300 BLK OUT Tubbs flat wire spring and the Kynshot 9mm hydraulic buffer. I have tried so many spring/buffer combinations and never gotten the Colt blowback system as smooth as the MP5. I have a rotary delayed blowback system from CMMG. It is pretty good but ejector springs don't seem to last.
What brand ammo? Suppressor? What length barrel? I used to shoot Winchester WB out of a 16" barrel with stock buffer and spring for M4 with no issues.
Have you checked your brass? The blowback system in an AR is designed with a certain amount of mass to hold the bolt closed during the high pressure phase. I was at a shoot where one of the shooters was using a H buffer with a Colt 9mm subgun upper. There was a loud bang and the gun stopped. In the center of the shell the side had blown out. Luckily for the shooter, the shell ruptured away from the ejection port, or he would have had shrapnel flying at his right arm. We looked at some brass he had shot. All of it was bulged in the center of the shell.
Scott
