Turbo Apex high altitude issues

[MikeTurboApex]

I've got an 06 apex running a MCX rear mount kit. I have the boost it kit as well with the XIC box fuel controller. Sled runs great and crisp in the parking lot and lower trail around 3700 ft but once I get up high, maybe another 1000 or 1500 feet, the low end is horribly boggy. No throttle response, hard to build boost because lack of power. Stutters and bogs.

Any advice?

 

[up-high]

IMO it's the fuel controller. Not sensing the altitude change and over fueling. Have you tested for boost leaks? Don't think that's it but you know?