In November 2005 I had the complete banks installed on our v10 powered 2000 coach at a cost of $1,795.
I was interested in a power increase, not expecting any improvement in fuel mileage. I did experience a very slight improvement in power but not as much as I had anticipated.
Later in June 2011 I added the 5Star Tune and did notice a moderate increase in power with less downshifts on mild grades. No fuel mileage increase in either case.
Had I not found a good deal on the Banks system I wouldn't have paid the full bore price to have one installed.
You most likely can get the same effect for less $$$$ by installing a set of Thorley or Gibson Headers coupled with a 3.5" exhaust/tail pipe with a high performance muffler i.e., Magnaflow; Dynamax or Flowmaster.
Best of luck & safe travels.....
Jim & Sherry Seward
Las Vegas, NV
2000 Residency 3790 V-10 w/tags & Banks System
2003 Suzuki XL/7 toad