I have finally finished my project on the 2uzfe twin turbo landcruiser after years of testing. made good power on dynodynamics [email protected] bar@7500rpm on 93 octane. the problem is the life of the valves. tried stock valves and supertech valves. all failed after 5 -6 races. they start to tap and suddenly car will stop. we took it to the garage and disassemble the engine to find that always one pistons will be severed damaged because of the contact of the valves. any experts who can solve this ? . what could be wrong ?. I use stock retainers and single valve springs which are good for 9000 rpm. I don't have any kind of problems like overheating or anything else. its only the valve scenario which keeps repeating again and again.