Bone-Stock 3.3L falling off Boost...

[Tilikum Turbo]

My completely stock 86' 930 engine recently has developed an issue:

Car starts normal/idles normal/sounds normal.

After boost comes on at 3K, it used to pull relentlessly to redline.
Now at roughly 5000 RPM, the boost/power simply falls off a cliff, and there is nothing left.

Any thoughts or suggestions. My first thought is to replace the fuel filter, which is about 4 years old.

Thanks!

[MichaelB]

Hmmmm. Maybe not enough information. Lets start with this: What is the boost reading before it "falls off" ?

[turbo owner]

Run your valves and inspect for broken head studs