wont rev to red line

[PeterSchroth]

Hi, I have a 1995, 993 with about 80K miles, I purchased about 6 months ago, runs fine except it will not rev to red line under load. When it hits about 5800 RPM it just flattens out, almost bogs, when you shift, after it hits 5800 RPM, it has the same loss of power for a few seconds then recovers and runs fine. The following have been checked, Cap and Rotors, both dist. working, New air filter and gas filter,both coils good, cleaned mass meter, fuel pressure OK. I don't know if plugs are original or not. The secondary air manifold had a leak, was fixed with a new Air Inj valve. Any thoughts of what to check next? Peter

[wvicary]

I would first test the output and pattern of the engine speed sensors with a oscilloscope and then look to the ignition coil control modules. The speed sensors can cause odd faults and become heat sensitive with age, it's often best to replace them and eliminate them from the loop.