It is at par with them (stock). Sirios have different powerband and emphasize top end. You need to understand that and normally have to gear them a tooth shorter in 1st speed and equal or some times a tooth taller in 2nd gear, than tha Novas. The right pipe is also important, they work very well with their own pipe, and others have had good results with the Novamega TPO4.
Allround they are very good engines for the Money. Mine runs as fast as the Novas at my track, and this last Sunday I placed second behind an RB Rody Tuned, and actually lost because he was better driver than me. But hey!! my engine costs $199.00 and the Rody is $340.00.
AFM