ok well i have been working onmy motor for awhile now off and on, this weekend i finally got a welder so i could weld up the exaust, i had blew a head gasket on break-in of a completely brand new engine. well i got it all done yesterday and i couldnt get it to idle smooth, it has been balanced and everything. i played with the timing forever and still no difference, i got out the carb cleaner and started spraying around the vacuum fittings and carb base, when i got to the egr block-off plate it made a wierd "pop" noise and started idleing perfect imediatly afterwards and it has been since, i got to looking a little closer and found the aluminum block-off plate was cracked, and one of the intake bolt heads is broken off, might have been the wierd poping noise i heard? i am going to pull the intake, and replace the bolt and new gaskets, would there be a problem with using 1/4 plate to replace my block-off plate??? also after spraying the carb cleaner and everything running smoothly now, should i be concerned that it all the sudden started working perfect??