I am happy to report that my new BigGun SDS system has exceeded my expectations for performance!!! WOW On my track at home, corners that were stock exhaust, second gear can be easily pulled in third with 14/51 gearing. With the stock exhaust exiting corners in second gear was an exercise in throttle control, usually with excess wheel spin and reduced control. Now I just pin the throttle in third, even out of very tight corners and it pulls almost perfectly matching available rear wheel torque with the optimal accelerating torque, not too mention the front end is soooo light now Such a problem. On top of that, cornering in third gears pushes me to have a higher cornering speed. Overall, it is even more fun!! (Keep in mind your traction conditions may vary and your fun factor may vary as well.) Now for the caveats with BigGun: 1) You need to buy the YZ silencer mounting hardware from Yamaha. 2) The pipe interfered with the shock spring – I run a larger 5.6 spring on the rear. Solution - I had to put an indentation in the pipe to clear the spring. 3) The pipe produces a lot of heat up high close to your leg and the fuel line & IMS tank. The pipe has about 1/8 inch clearance from the fuel petcock on the IMS tank. Hot pipe close to fuel Solution - I fabricated an aluminum heat shield for the pipe. Major labor, but it works. 4) The competition core is about as loud as stock. Potential solution of a BigGun quiet core spark arrestor is still on back order. Eric in WA ++++++++++ ’99 WR400, YZ timing, BigGun SDS exhaust, Jetting: 48 Pilot, screw 2.25 turns out, DVP needle clip # 4, 185 main (500 ft alt). Air box lid on without the snorkel, IMS Tank, YZ Seat, Acerbis Handguards, Scotts Steering Damper, Renthal Bars, Devol Rad Guards, Dunlop 755F & 756R Tires ’99 Polaris 400 Scrambler –“Trail Couch, Toolbox and Lunchwagon”, ’99 Honda Z50R, ’97 Honda XR70R, Kubota L275DT and an assortment of farm equipment.