1997 Eclipse Iusses turning over

I have a 1997 Mitsibishi eclipse GS. I bought it used with 121,000 miles on it and a week later the tensioner broke off the side of the block causing the timing belt to slip off and the motor blew. After a year of doing 3 motor swaps because a galley plug kept leaking in the motors, this one finally worked right but there seems to be a few small problems. My first main one is some times, mostly after the car has been running for a little bit and I turn it off, when I go to start it back up the engine starts to turn over but then it stops and I hear a noise like a belt is slipping or something. Could it be the timing belt? Also I some times have problems putting it in second gear. I will step on the clutch all the way and it starts to go into second but won't go in fully. Its a brand new clutch and flywheel so I am stumpped. Could it be my transmission? And lastly when I did the swap I got new spark plugs and wires and when I down shift to start slowing down I hear a lot of popping. Could it be one of the plugs? Or is that normal. I hope some one can help me I have been everywhere and no one can seem to tell me what is happeneing.