There are several things that M20's don't mix well with. Consistent high RPM is definitely one of them. Rockers like to snap, and unless you have the IE HD ones, plastic deformation is a constant concern with them...
Also, you really, really don't need a cam until 450hp.... This is well documented on E30tech. It is 100% not a "necessary" part. It certainly doesn't hurt, but not needed...
Taken from the E30tech Turbo E30 FAQ
Q:
What camshaft will work best for my turbocharged E30?A: There is no universal M20 turbo cam shaft. What cam shafts that work in the engine is determined basically by three things:
- Manifold design
- Turbo charger size
- Pressure (boost and back pressure from the turbo+manifold)
This affects the duration of intake/exhaust valve opening and how much overlap is possible without affecting cylinder scavenging and filling.
Ultimately, the factory cam shaft works very well on a turbocharged car as long as all parameters seem normal, like increasing boost results in the expected power increase. If that is not the case, many things could be wrong:
- Too small turbine (excessive back pressure)
- Intake or exhaust leaks
- Malfunctioning wastegate or boost control
If you're looking for insane power increases, up to 500 crank hp out of what was originally a 170 hp N/A engine, then you better do some research and talk to a cam grinder. You should not expect low-end grunt with a turbo that flows enough for 500 crank hp on a 170 hp N/A engine.
AND backed up by a STOCK CAM M20 Dyno figure, up to 7200 RPM, which is a lot farther than I would consider the safe zone for stock rockers, This guy had IE HD's

Also, Found the photo
