I had the same problem on my 535i. My dyno chart went like a sawtooth pattern. It was my speed sensor down on the bellhousing. It generated enough of a signal to start the car and run it, but the computer would hunt on open loop. It actually measured open on my meter, when it should be 1000 ohms. Give this a check, because our numbers were almost identical, with a dip at 4800 rpm.
Kevin
Well here they are and they don't look too good. The guy was saying that he thinks my fuel mixture could be off. Probably running too rich. The chart looks like a heart monitor! It goes up and down and then a HUGE drop in power right at 4500 rpms then it picks back up at 5000 rpms. I always felt that my car was not putting out the power like some of the other 535's I have driven. I need help from you guys. What do you think my problem can be? He said that the chart lines should be more of a straight line and not up and down like mine was. If it is running to rich how do I adjust the air/fuel mixture? The only car I was able to compare to was a 1989 e34 535i. And he was putting out way more power than I was. I will get his figures later. I know they have about 20 more Hp that we do. Oh ya has anyone else ever dynoed their cars before? I am curious to see how mine compares.

1st run
Hp 148.1 Torgue 164.2
2nd run
Hp 146.7 Torque 166.0
3rd run
Hp 149.2 Torque 169.7
4th run
Hp 149.6 Torque 175.1

As you can see the last run was the best one of all. And if you take the Hp and multiply it by 1.21 you should get the Hp at the crank or the flywheel I can't remember. But it equals 181hp. Which is 1 away from stock... Not good.

Jay
1988 535is
TDH Intake
SS Exhaust
3.73 LSD
8mm wires