Yes, these mods will transform the bike's power delivery making it far more flexible and nicer to ride. However, they won't do anything for the fire-breathing exhausts, in fact they'll make it worse!

Flaming exhaust(s) is/are normal. It is just unburnt fuel igniting caused by the introduction of fresh air at the exhaust ports downstream of the valves. The air induction system (AIS) and ECU controls this and opens a valve when the throttle is snapped shut, or the engine is on the overrun, or under cold start conditions. If you don't like the popping, banging and flames then it is very simple to block the AIS system's supply of air which originates from the airbox with no ill effects.

Read this: http://www.xt660.com/showthread.php?t=11113

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