Hesitating/Jerking/Kicking...HELP!!!!

Recently I have been having problems with my GM hesitating/jerking while driving. The problem usually happens around 40 mph, and after jerking it, it just kicks it into gear. It also kicks back when I apply the break.

It's a '94 MGM, and a year ago the engine and transmision were replaced. It has crome 17'' Rims, with spacers on the back (I am not sure if this could be the cause). Also, when I turn up the sound (2500 watts, two 12'' subs), it used to kick out the fuel pump button in the trunk. I replaced the whole thing (not the fule pump, but the controler in the trunk), and it doesn't do it any more, but it still runs rough when i turn the music up.
Also, what do I need to do about my AC, since the engine has been put it, i havent had any AC.

Please help, I just love this car...

P.S. The fuel filter has not been replaced since I got it, which is 7 yrs ago. Front brakes are brand new, transmission fluid looks good, it does burn engine oil but not a lot.Spark plug and wiring is also almost new.

Thank you...

I think you may have "nailed it" in your "P.S." - no fuel filter change in 7 years? I would do that IMMEDIATELY!! Less than a $20 part and less than 30 minutes to do! See what happens after that - may also try some SEAFOAM in the gas tank and thru the PCV hose. There are instruction on this site if you do a "search". MB

The hesitating and kicking I can do without, but a jerking while driving sounds alright, even better with a working A/C this time of the year.

Recently I have been having problems with my GM hesitating/jerking while driving. The problem usually happens around 40 mph, and after jerking it, it just kicks it into gear. It also kicks back when I apply the break.

It's a '94 MGM, and a year ago the engine and transmision were replaced. It has crome 17'' Rims, with spacers on the back (I am not sure if this could be the cause). Also, when I turn up the sound (2500 watts, two 12'' subs), it used to kick out the fuel pump button in the trunk. I replaced the whole thing (not the fule pump, but the controler in the trunk), and it doesn't do it any more, but it still runs rough when i turn the music up.
Also, what do I need to do about my AC, since the engine has been put it, i havent had any AC.

Please help, I just love this car...

P.S. The fuel filter has not been replaced since I got it, which is 7 yrs ago. Front brakes are brand new, transmission fluid looks good, it does burn engine oil but not a lot.Spark plug and wiring is also almost new.

Thank you...