A month ago I posted regarding a significant loss of mpg's (5-6) in my V70, as well as a loss in power, and an occasional "main catalyst low" CEL. I listed the things that I had done thus far to troubleshoot. I'll list them below once again.

1. Cleaned my throttle body.
2. Replaced entire PCV system
3. New intake gasket
4. All new vacuum hoses. Everything surrounding intake manifold, and all hoses routing back to turbo. All lines are brand new.
5. New turbo control valve.
6. New injector seals
7. Disconnected battery to reset computer
8. Checked for sticking calipers and parking brake
9. Checked air tire pressure
10. Turbo can provide full boost pressures
11. Compression check, all cylinders about 185 PSI
12. New spark plugs

There was some great feedback on the original thread, so I took some of it to heart, and besides the ample CAT reading I did, I also did the following.

1. Had a vacuum system and exhaust system smoke test done. No leaks found.
2. Had car connected to VIDI. O2 and mass airflow sensor responses are normal. Long term fuel trim was within 2%. Not sure what it means, but the tech the car had not been running rich or lean.
3. Had an exhaust back pressure test done. Back pressure was from 0-1 psi at high RPM's. The mechanic said it was normal.
4. Alignment was done, no significant toe-in of front wheels.
5. New fuel filter

I'm tossing around a few revised theories and hoped for some feedback.

1. CAT is still bad, but not blocked.
2. Exhaust shop tech said it could be low fuel pressure
3. Partially blocked injectors
4. 4 of 5 coil packs still original (150K)

Other then that, I can't think of another system that could contribute to mpg that I haven't touched.