Blow By
 

I have a sr20 black top s13 and im runing about 18lbs of boost i have good compression but when i get on it hard i get alot of oil in the catch can what may be the cause of this

i just noticed...

what blacktop is it?? the T25 or the T28??

18 is unsafe for either...

which turbo is it??

the t25 yes i know its unsafe but its been runin that way for 2 years it the gt30

what?? is it a GT30 or a T25??

its the s13 black top t25 with a gt30 garrett

excessive blow by means you are either getting way to much cranck case pressure and or your seals are beginning to go

perform another compression check..

also you are kinda confusing when you say t25 GT30 lol i get it but yea......