325is 87 engine lag/no power...help

hello i have a 87 325is and it has some problems well i only piad 500 and its in good sshape with 80k on it .well it has no bottom end at all and it runs realy rich.and when i hit the gas it stumbles and almost dies ....it has good fuel pressure and good (plugs/wires/cap rotor) but still runs bad.......:banghead:

First, take the rubber bellows off of the throttle body and see how clean/dirty the throttle body is. If she is dirty, buy a can of throttle body cleaner and spray in (engine off) and wipe out the gunk. Next, buy a can of BG44K fuel system cleaner (may be hard to find but any independent auto repair shop should sell it, this stuff is pricey, may run up to $25.00 a cannister, but that stuff will clean your injectors, valves, etc like nothing else. Also, check the accelerator cable linkage at the throttle body and make sure it is tight, not a lot of slack.

well the last owner changed the rearend and i think he might have put the es rearend in the car .how do you identify what rear end it is?

Do not know about BMW differentials (if they are tagged with ratio) but here is the old school way. Get rear end of car off ground, release parking brake and put car in neutral, make a paint or chalk mark on the outside of tire and also on the driveshaft (where you can see them) then turn the tire by hand and watch the paint marks, count the number of revolutions the tire makes versus the drive shaft rotation and you will be close.

well i pulled the timeing belt off it was realy bad lots of slop and it was going to brake .well i got that all back on and i stil have a lack of power but its not that bad ....still cant get a good take off ........i got a free flow exhaust could that do it?

How long since the valves were adjusted (this is a solid lifter, valve adjust engine just like my '90 325ic). This could also be a problem if the valves needed adjusting. Again, take bellows off of throttle body and then using your hand, rotate the butterfly in the throttle body using the accelerator cable linkage and see if it is smooth all the way or perhaps initailly sticking and then breaking loose (lube all of these points with throttle body cleaner).