I have just bought a R32 and it does the same thing. When I first drove it home it would start misfiring at 3000 rpm but after mounting the ignitor so it wasn't floating on top of motor and fixing dodgy wiring it now gets to 4000-4500 rpm before misfiring. Also when I tried to give it a squirt it reached 4000 rpm in 3rd and just wouldn't rev any harder. Didn't misfire or anything, just wouldn't rev any harder.
I have been told to check spark plugs, coil packs, and the wrap tape round the spark plug technique. Aswell as being told it could be crank angle sensor, oxygen sensor, blown head gasket, or even pistons and rings.
I have just grabbed some standard plugs and I am going to check coil packs as I can't afford those yet and have it booked in for compression test.
Anymore advice I can be given would be highly appreciated!