Originally Posted by Chris Peralta

Well there are two reasons your C6 is getting poor fuel mileage. The first is the JP1 pipe, while the pipe does make decent power it makes an RB an all out fuel hog. You would be doing yourself a huge favor by getting the 2045 pipe.

Next thing holding back your run time is the MBX5, that car is very heavy and has an inefficient drive train. With a 2045 you could probably get up to 8.5 minutes on the MBX5 but if you go back to the 6 you might even see those runtimes go to 9 or 10 depending on track and driver.

As far as getting a B10, that engine is a great engine but is not going to be a ton different than your C6. if the C6 is still in good condition you can save some money by sticking with it and getting a 2045 pipe, and both 192 and 198 headers.