What's the history on that motor? Have you dicked with the injectors, manifolds, fmic, cams, etc?

You're probably on the right track with the timing. To double check yourself, the CAS should be generally in the middle of it's adjustment range.

TPS sounds fine.

Falling on it's face after 4k sounds like a boost leak. Check your couplers and vac lines.

Check the ECU codes with the LED and screw on the back.