So I found a leak (cracked gasket) on the Exhaust Manifold to turbo gasket. Does this constitute to HP Loss? It's a nice stream of air blowing out, I can hear it standing outside of my car while in idle.

 

Yes. Exhaust gasses spin your Turbo. If it's not getting the full flow, then its not going to spin as fast. If its not spinning as fast, its not compressing as much air as it efficiently could. I'm sure its effecting your spoolup time, which alone will hurt your power.

Get a new gasket, get a new bolt (you said its stripped in your other thread), and fix the issue.

 

Because its making boost, whatever PSI we want but it's not making any power, so it could be its cavitating or just not efficient enough.

 

Do you have any datalogs to see if its actually holding the boost its set at, or if its just spiking to it and bleeding off?

Its also creating an exhaust leak, before your O2 sensor. That's going to throw off your A/F ratio. So tuning the car with a wrong A/F reading is going to throw off the tune, as well as hurt your power, and eventually could cause engine damage. Your going to read much leaner than what the actual enging is seeing. Your tuner is going to add more fuel to richen it up, or reduce timing advance. That is a loss of power.

 

I don't know, he told me that he even tried tuning it with aggressive timing and it just did not net any HP, 16hp over pump on E85

 

Definitely get that gasket swapped out ASAP. You'll see gains on pump as well.