That's odd that it bothered yours. My car picked up 6-7whp with the airbox opened as you describe.
Mine was on a lower reading Mustang dyno ~8-9% lower than the local DJ.
Closed it made 120whp and 129wtq completely stock.
Open it made 126whp and 131wtq completely stock
I'm currently developing something that made +17whp and +17wtq over the baseline numbers without any tuning, and NO CELs :banana:
What is it you're developing if you don't mind my asking?
The reason I ask is because without the tune there is only so much you can try to pick up power wise before the ECM will "re-tune" to stock power levels.
Well I really hope you where not messing with the wastegate to pick up the extra power, you'll blow a turbo seal in a matter of days and be ready for a big turbo upgrade sooner than you had hoped.
Well I really hope you where not messing with the wastegate to pick up the extra power, you'll blow a turbo seal in a matter of days and be ready for a big turbo upgrade sooner than you had hoped.