Why does the a4 2.8 make 10 less bhp than the a6 with the same engine?

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A re-routing of the exhuast and a different ECU. This is what my dealer told and I looked and looked at an A6 the motor as well as the underside (it was on a rack) and the only difference I could see was a dual exhaust. I couldn't see a difference in the exhaust manifolds but I could be wrong.<p>Damon<br>98.5 2.8 Avant QMS, AMS Chip, cat back, K&N, H&R,Bilstein, 18x8.5s, Recaro SRs