Whats your riding level ??? (beginner, amatuer, pro). If your not just riding the heck out of it, racing, or making money with your bike, go with stock type components. Keep the compression the same and use stock valves. Higher compression may force the use of race gas and stainless aftermarket valves generally will require new springs, seats, shop to put it all in, etc, etc, $$$$$. Aftermarket Ti valve usually start out twice as much and up over stock. With stock components and regular maintenance, your bike should run well and be more reliable. Use the money from not buying high priced racing parts and maybe do the water pump cover upgrade (I believe this is the same motor used by Suzuki and has the one piece water pump/oil filter cover-if it has not already been changed). Use stock components and maybe add an aftermarket exhaust and a jet kit. You would probably notice more of a differance in usable power and these parts (usually) don't wear out. Something else to concider when trying to improve a bikes performance, it does not only include the engine, suspension, bearing, linkage, brakes and tires all fall in. Look over you bike and see if it could use any of these things. GOOD LUCK, and yes, it wouldn't hurt to replace the timing chain and tensioner. Also check any timing chain guides for excessive wear.