Is it possible to install 4" core thick intercooler on EG civic without ugly bumper modefication or 3" is max?

 

Definately. you have to remove your bumper support. and mount it as flush as possible to the core support.

 

my buddy just tried fitting his 4" intercooler on a EG and couldnt get his bumper on. The had is as far back as possible with a fullrace twin scroll t4 cause the 44mm wastegates were hitting the intercooler. He switched to a 3" and solved all problems.