Boost stuck at 10psi in last gear

[Jdiddy2k4]

My car is an auto and the mods are in the profile. When it gets to the last gear, the boost will stay rock solid at 10psi and won't go higher. Through all the other gears it is fine, but as soon as it shifts to the last gear no matter if the boost was just at 15psi it will fall down to 10psi and stay. I have a leak at the throttle body(shaft seals i think) Would this cause this problem in only the final gear?

 

[crimsondragon]

What RPMs is the car in by then?

 

[Jdiddy2k4]

Haven't really checked. I will have to get back to you on that.

 

[1bad92awd]

I would not imagine that the throttle body seals would cause that problem ONLY in the last gear. Depending on what rpm your at by then, the turbo may not have spooled all the way up. That is even a bit of a long shot thought considering its just a small 16g and you drive and auto. Unless you let off the gas, your car should not be losing any boost during shifts.

 

[Jdiddy2k4]

Yeah it will hold the boost through the shifts in all the other gears but as soon as it hits that last gear something is limiting the turbo rock solid at 10psi. I can't tell what the rpms are by then until I get the car back from the shop though.

 

[Jdiddy2k4]

I have checked and in last gear the rpms start at 4k when I step on the gas and it holds at 10psi rock solid all the way through. It also does this if I try and take off from a 30-40mph roll. Any ideas?