As far as I know ALL tuners recommend that you use high flow downpipes (catted or not) with an FBO tune. If 5-8whp is all we can get between catless aftermarket and stock catted downpipes then why do we all bother?
I have never seen a tuner say that you can use an FBO tune with stock downpipes. If that was the case I'd be very happy and I'd go right outside now and change my tune from Cobb Stage 1+ to Stage 2+ and save a heap of cash.
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