I purchased a 2004 350z approximately 5 weeks ago and I'm having trouble getting the motor to aggressively after 4000rpm in any gear. Car runs fine under 4000 rpm. I have no CEL codes. So far I have replaced the MAF, CAM sensors, Electronic Throttle Body and most recently I've replaced the factory ECU with a Haltech Platinum Pro.
The problem still persists, I believe the problem may be mechanical. Any Ideas?

 

Limp mode?
What exactly is it doing once it hits 4K, just gives out like hitting redline or...?

 

Limp mode shouldn't allow it to reach 4k RPM.
I was going to be a smart *** and say it was VDC kicking in, when my tires slip in 2nd at 4k my z loses power too because VDC is doing it's job and keeping me in check, LOL.

 

so you are just throwing random parts at it... with all that money, you could have taken it to nissan for a proper diagnosis

 

What trav said seriously, one $90 visit would have led to an answer and money saved.

 

Post a video if you can or as mentioned above, go get it diagnosed.

 

The cat's might be going bad. You will have a great power loss with bad cat's.

 

Thanks for the replys gentlemen. I discovered the problem to be an exhaust blockage.

 

Was it in the cat? If so what do I win??? Lol man I am good! I have been working and rebuilding cars for far too long.

 

where I. The exhaust I'm having the same issue