The road tests carried out by motorcycle magazines, if they are anything to go by, always showed less BHP for the later models, the ones with the bigger fuel tank (the earlier ones had a 16ltr and the later ones 19ltr) the reason for this was said to be down to the different sizes of the airbox. It meant that too be able to accommodate the bigger fuel tank a smaller airbox was used
Pre-1999 (not pre-2001) models output a bit higher for fact, and all dyno tests printouts that I saw (not from bike mags) did prove it, ibut we know how much bike mags riders really know
Airbox on post- 2001 is exactly same as on 1997, and I do know it for fact because I have installed tank from 2004 Storm on my 1997, and even more sure because later I bought 2002 airbox off eBay to play with cutouts etc. Tank made bigger by extending fron-top part a bit and by using completely different petcock addembly - on post-2001 bikes petcock is different and bolted to frame, so that bottom of the tank in rear part is lower than on 1997.
The reason 1997 model was most powerful possibly because they did not care about emissions at all... and as consequence - I heard few versions, one about ignition map and one about very slight change of camshafts profiles. Story about camshafts is something that I tend to believe more.
ill see if any one does dyno runs here and let you know how it affects the power.
