I've noticed that if I build boost and get in to any kind of rpm's (4k+) its almost like the engine just stays there as if it were in neutral and doesn't really start falling down on rpms or engine braking, but as soon as you touch the brakes and it gets below the 4k its like a switch is flipped and it will start braking.

Any idea on where to start?

 

Try explaining your issue more. It is confusing. Sounds to me like maybe your throttle plate is staying open a bit when you let off the gas so it is creating a feeling that you still have your foot on the gas slightly even though you have foot off the gas pedal.

What gear are you in and and are you depressing the clutch? If you are in a gear and you let off the throttle then the rpm has to change in sync with the mph. The transmission is connected to the engine so there is no way it could move independent unless your clutch is slipping or you have the clutch pedal depressed.

 

You described the feeling perfectly.

 

I would suggest checking your throttle body then for carbon and any sticking during movement. Also check the throttle cable as it could be kinked especially since many people re-route them. Although unlikely you should look at the gas pedal also for smooth pivoting.

 

Thank you, I will check those two.

 

No dice.


Say I am in third and I get in the gas and build full boost and run up to say 5k rpms and let off the gas and do not touch the clutch, in all of my other vehicles, the engines compression will start to cause the car to slow down and rpms fall.. How ever right now, its like when I let off the gas, the car has been put in cruise control and the rpms stay the same and it doesn't slow down any at all, but then after applying brakes and bringing the rpms down to around under 4k (still in third and been on the brakes) its like then the car catches up and starts to lower the rpms and compression brake.

 

Search for throttle hang. It's a well documented problem. You will need to modify several tables to tune this out.

 

+1 to you.

 

Is this something that can be taken care of with a flash? Or is this going to actually require dyno time?