Ok, so I have replaced the turbo cartridge with a MR Turbo one, now under boost at 3500rpm in 4th the car shudders and looses power. So today I tested it out after a few adjustments and hit 4th at 3500rpm and the car severley lost power, kinda like chug chug chug back home (1 minute drive), then I popped the bonnet and there was coolant jamming its way back into the resevoir under some type of pressure. There was also a knock in the what sounded like the engine, but from the side of the car also sounded as if it was from the gearbox. Sat the car for 1 and half hours, then fired it up, no knocking noise and coolant was back to normal, took it for a light drive, it seems ok but I know the problem still remains, if I boost it up it's gonna pop for sure. Any idea's. p.s. I am taking it to a mechanic to check it out, definitely to Ford to run the diagnostics.