Thats cool, Raymond I was the young dude you bought the blue duramax off of. Don't know if you new that or not. Wish I could have BS'd with you at a few pulls last year. You must stay mostly south east as I don't see you around the central area?
A mixture of both or when you have to build a engine. I couldn't shift my stock engine at 4200rpms anymore becuase the valves would float. I was just shy of 39 psi. My engine has seen 4850 numerous times but only had 49,250 miles on it when i pulled it out. Over a period of time with bigger turbos + high rpm's they just got weak.