I just came back from the track
I noticed my car's rpm won't go any higher after 4000 rpm
what's wrong?

 

is that in any gear? I don't understand, is the CEL on?

 

when you say the RPM wont go any higher than 4000, are you literally saying the tach doesnt move at all after 4000, or is it very hesistant to move. If it is very hesistant to move, but does move very slowly, it is normal. When I got my 84 trap speed, my tachometer seemed like it was stuck,(for the sake of description) and I had a very hard time pushing power after 80mph. But on the way back, after it had rained and cooled down a bit, I punched it on the highway and the car definitely moved a lot better than on the track. I'm talking about post 80mph here...

It seems like the weather condition manifests itself very visibly on high speeds.

 

I had this problem pretty recently with my car. The car pulled in 1st and 2nd, but in third, it felt like I was hitting fuel cut at about 4.5K. Turns out I had a really clogged fuel filter and the wrong plugs in the car. Guys at the store sold me the plugs from an 86 300ZX Turbo instead of the newer 300ZX plugs I had requested. After fixing those problems, the car ran fine.

 

I changed fuel filter not too long ago
and I changed my sparks too
herm...
do you get this problem when you are at the track shadow
?

 

I think I have the same problem. First and second are fine but then third seems like it slows.I usually pull hard on third. I have NGK Plats that I put in about a month and a half ago and fuel filter hasnt even been in for 9k miles. My friend said he heard something pop when I was driving next to him... I guess ill check it out.

 

no one knows why this is happening?
does this happen to 5-speed?