Yes, for the most part they are permanent. This is why some problems will go away never to be heard from again. Like the cats. The OEM ones suck and the Hyperflow cats rock. They have a lifetime warranty and are within 4% of straight pipes. You never hear anyone ***** about those anymore, but go back a few years in the posts and you will see it all over. The headers are another item that almost nobody would replace with OEM. Valve guide issues will be the same way. They will eventually go away when all the bad ones have been identified and replaced. In 15 years all of the problems will have been identified and replaced and the 355 will be a classic. I'm waiting for someone to make a good aftermarket solution to the timing belt to spread out the engine out time.
After how many miles? What were the symptoms you experienced that prompted the valves to be done? Just curious. Thanks
