Z32 Stumble/misfire @ high rpm/high load

[thejones16]

My tuner just set up my EMS on my 300zx and he's hitting a wall after 4k rpm in boost. I noticed my fuel pump making more noise than usual after the tuning, and because it has over 130k miles on it, I decided to pick up a new one to be on the safe side. I have yet to install it (project for this weekend), but I was hoping some of the experienced tuners might be able to chime in. Also, the CAS disc has not been swapped out yet....could that be the problem? The car runs great in all other regards, but when it hits high boost over 4k rpms, it stumbles and misfires terribly.

Things that have been tested:
-spark plugs look good and have less than 5k miles on them
-Compression test shows low compression on 2 cylinders...would that be the cause of this problem? I was hoping it would just mean less power output
-battery voltage looks good on a brand new optima red top
-new EFI harness installed less than 5k miles ago
-new canton racing fuel filter installed when 740cc injectors were installed
-new dual intake setup running on a GM MAP sensor


Any ideas, suggestions would be much appreciated.

[thejones16]

Ok, replaced the fuel pump today and the problem is still occurring