engine swap 1976 M42 Swap Rev Help

[ziddygrew]

So I have a 76 2002 with an E36 M42 swapped into it and for some reason it won't rev past 4k RPM. What could that be? I've called a few shops and they told me it's either the coil packs, timing is off, or it's the crank position sensor. I figured it's not the CPS because it starts, runs, and drives, just doesn't rev past 4000. Anyone else experience this or know what could be the problem?

[ar_kid]

Put a timing light on it (and if necessary a timing mark), check to see if the mark moves as you rev it up. It could be that the ignition system has gone into limp-home mode and is running a fixed advance timing.