This is starting to become a headache and it's getting more and more frustrating. Check this out I can get in my car in the morning and while it's cool it's fine and I am ready to go to the track but the more I drive it when it gets to around 180-190 it will not go over 4500 RPM'S I have heard it all from the radiator fans air messing up the mass air meter, vapor lock(which I don't know much about but a guy told me it has to do with the fuel line becoming to hot), O2 sensor's, throttle postion sensors. I was told it was the fuel pump and it's starving so I went and got a 255 fuel pump from anderson motorsports and it's still doing it. I need some help......I have taken it to the shop twice, the problem is when they test drive it or take it out and the morning it's been sitting and it's cool, tommorow I may drive it until it does it and then take it up there now that I think of it because it has yet to do it while it's in the shop they think I am crazy I think they love the car but they don't drive it long enough to see what's really going on if anyone has any suggestions please let me know. It does it when it' gets to operating temperature it doesnt' before it's everything you would want then it starts acting funny when I get on it and it stops power around 4500 RPM now if I shift the power comes right back I think it's something with that mass air meter...but hell I don't know

 

vapor lock is centralized to carbed low pressure applications, efi rarely would have such an issue since fuel is under constant high pressure, have you driven car with a fuel pressure gauge attached to car to see what is happening at that rpm??? fuel pressure may be dropping off due to a restriction , filter maybe??

 

I will check on it tommorow but when I put the fuel pump in the car I change the fuel pump also but thanks I will look into it I can rev it up after it get warm and I'll watch the fuel pressure from under the hood tommorow..thanks for the suggestion

 

Check this out I drove the car when I got off of work and went over 130mph never got above 190 and it never pause or hesitated one bit. It has to be something with the air because when it's cool it does what it's supposed to do but when the air is hot or humid it acts crappy...is this possible that the air temp is affecting my car this much that it can make it fall down at 4000-4500 RPM then when it cools down to the 60 or 70's it doesn't where should I be looking at too solve this problem...thanks in advance

 

you need to test your IAT (ACT) sensor and make sure its not messed up.

typically, if the IAT sensor is messed up, the ECM will read it as -40°

 

I cant help with the rpm but when it gets hot or humid out, that will effect performance. Heat kills horsepower. Thats one reason why using an open element air filter under the hood isnt a good idea, it ingests all that hot air under the hood. Even if you dont use an open element, just being hot outside will effect the power.