sputtering

My friend brought me his 93 3.1 regal to work on. He does not have allot of money to throw at this thing so I am trying to not throw parts at the problem. What the car is doing is sometimes it stalls when put into reverse. Sometimes it will start and dies right away. If the RPM's are brought up in park it sputters above 3000 rpms. If the car is driven it sputers and acts like it is going to die. Sometimes when the car is started the engine will sound smooth up front but sounds like a hemi out the back. The car appears fine in park at lower rpms but once engine is put under a load it acts up. I have cleaned the TB and the IAC. I have checked the front plugs and they look pretty clean. Could someone point me in a direction on where to looking or what to start replacing

i don't know if there is a length of time to respond but check your catalytic converter and egr..