I've done the Big Bore Kit (and Bub slash cut exhaust, and Mikuni carbs). The difference in power is EXTREMELY noticeable. More so than the difference from going from stock to new exhaust and removing airbox. I did my work in stages, so I could feel the difference of each modification. As for reliability, in some senses only time will tell. But I will share this with you: I had the BB kit dropped in, took it out each night for a week to get through the break-in period, and then headed out for an 1,100 mile weekend far from home with the bike (not without a little concern over this reliability factor). But the bike did fine. Hauling me and all of my gear for 4 days. Highway blasting from DC to NY, and then back roads and hills through NY state. The bike was great. No oil useage, no hiccups in running, and definitely more power. I would do it again - the only caveat being the cost - it costs a good dollar. But if you have the money and are willing to spend it on this, then I would have no reservation recommending it. There's my 2 cents....
