turbo 2.8

I have a 4.0 with a Vortech and custom fm intercooler 2.87 pulley
the car was boosting great in 1st and 2nd gear about 11 #s
the problem was when i got in 3rd and 4th gears , 3rd would see 8#s
and 4th only 6 #s WTF !!!!
checked for leaks , all seemed fine , checked vacuum hoses , good
looked for belt slippage found some dust , so i bought a bigger tension er pulley
but still same issues ! so now im banging my head ! why , why , why !
so was looking at belt when i noticed the sc pulley was grinding on something, there were grinding marks on it .
it was the egr pipe running just behind the pulley , The weird thing is at idle there was
a 3/16 " gap , so i assume that under load something was moving 3/16" and making contact , i checked all the sc mounting bolts , all tight , checked the sc pulley , it was tight
so i made an adjustment to the egr pipe , now there is a 1/2" gap
took it down the road for a shake down ta daaaa ! 11.5 #s of boost in every gear !!
happy its fixed , but curious what is moving 3/16" seem s a little excessive for flex