When you hit the boost limiter it does cut hard, as said. just try turning the boost down a little.

After having my s1 chipped... i was running 14psi but when i had certain electrics on, lights, rear screen etc... i could only run 11psi before it kind of hit a flat spot and wouldnt rev any higher but if i turned the boost down so it was at 11psi to start with it was ok. I knew it wernt the boost limit cos it was chipped and i'd been running higher previously.

I took it Well Lane and they changed the plugs, they put champion c59c in. It solved the problem. and i could run higher boost.

Could be the same?!....