Grand Prix 500
Main Motorcycle: Triumph Thunderbird
Join Date: Sep 2010
Location: Central Texas
Other Motorcycle: 91 FXLRC
Extra Motorcycle: 90 HD Sportster 1200
This entire thread is very interesting... to the point where I consulted my local "expert" Paul who has been working on metrics his entire adult life... He is also the guru on the DYNO at our local dealership.
Now he has never tested a TBird but has tested several other bikes on the DYNO, Goldwing, HD Big twins, and a couple other crotch rockets... He's done the tests with stock filters, K&N and another "SHOP" brand (foam) that they use... All but the older HD's were EFI's.
His results are pretty convincing, that unless you have an aftermarket control module (like the Power Commander) and put the bike on a DYNO for a custom tune... The difference is negligible... He said the biggest change was with a Goldwing and he was only able to gain a couple of HP and probably improved the gas mileage. The other bikes improvement with stock tunes were barely measurable... except for maybe MPG... while some improved and others were less.
So having heard Paul give his professional opinion leads me to believe that unless I have to replace the air filter... it is going to stay stock... Then I will replace it with something respectable but not over priced....
To each their own... and everyone has their own (opinion).