Have a ba xr6t and have been chasing extra power out of it. It has 3" dump pipe int twin 2.5" exhaust, walbro fuel pump, 440cc injectors, growler CAI, HD valve springs, FPV intercooler. Was tuned and got 366rwhp at 10 psi.
Here is where the problem is. When boost comes on it spikes (up to about 15-16psi) and straight away drops to 10 and stays there. Tuner said to get more a manual boost controller was needed. Put one in, same result. Tuner said it must be the wastegate actuator, bought a 12 psi actuator but before putting it in the turbo died. Replaced the turbo (new one had 12psi actuator also) and it is still doing the same thing, cant get more than 10psi.
Help please

take it to a different tuner. If he's having that much trouble & guessing, he simply doesn't have the answers you need

Figured that they may not reallly know what is going on, but cant afford to take it to another tuner right at the moment.

Check the tension on the actuator rod, sometimes they are over-tightened and and don't have the required movement.

let us know how you fair.