BMW: 325i ISSUES!!!, bmw 325i, car idles

Question
Hi, i have a 1988 bmw 325i convertable, 5 speed.  The car idles rough, has almost 300,000 miles(not sure if it was rebuilt),  when i get to about 4500 rpm , in any  gear, the car loses power and then the exhaust starts popping, then it will run past 4500 rpm fine, but when you shift gears it immediately starts popping.  Also, when i am driving the speedometer will just stop working from time to time and drop to zero, is this the speed sensor on the transmission? engine sensor? any help would be GREATLY appreciated, thanks

Answer
Bill,
 Without seeing the car and driving it personally I can only guess as to it's problems.  I would suggest a tune-up on the ignition system, and that will likely help some (especially with 300k on the clock).

 The speedometers and clusters in general are notorious for giving electrical failures.  You can take it apart and clean the contacts in hopes that it will fix the problem or just replace the whole unit.

 Good luck,
 Josh