Opening the throttle butterfly admits more air into the engine, but unless the fuel delivery system can, or will, provide that extra fuel, more power will not be produced.

It could be the filter/regulator, etc., or it could be the computer is not receiving the right input for it to command more fuel.

I would hook up a fuel pressure gauge with a long hose so you can route it under the windshield wiper with the hood closed, and drive the car while watching the pressure. If under full throttle, you begin to lose significant pressure, you know you have a mechanical supply problem so that the pump/filter/etc. cannot keep up with demand.

I have one such dedicated gauge in my shop just so I can do that. Very handy. You can make one up at Home Depot for about $15 total.

Bob

My '87 535is automatic seems to produce the greatest power when the pedal is about halfway through its range of motion. Pushing the pedal to the floor produces noticeably less power. Ease up on the pedal and the scalded cat effect comes back. The ideal position seems to be at almost exactly the point where the transmission kickdown occurs. Any thoughts?