What's a good way to clean the inside FMIC? What's the best solution to use to remove all the oil/gunk? Im seeing 140 AIT and Im not even boosting. I have 3.5 ETS over a year old

 

Cap one end, pour in some gasoline, cover the other end, shake/slosh it around, and drain. Repeat until the gas comes out clean. Let it air out and dry thoroughly before reinstallation and of course perform this outdoors in an area with good ventilation.

 

gas as in fuel? I was thinking soaking it on bleach. Cover the cap on the other and and fill it up with bleach to desolve the grease/gunk inside.

Im just not sure if they will/wont harm the core inside

 

S2kracka is right. Nothing cuts that nasty oil stuff as well as gasoline.
By any chance are you using the stock airflow sensor with an open cone filter? If so, heat shields and ducting will help as well.

 

Don't use gas. It will leave residues. Pick up a gallon of Toluene from a hardware store (~$10) and slosh that around inside. MUCH better at cutting grease and oil and will evaporate very quickly if you have any left in there. (Plus it's around 112 octane)

 

and then mix toluene and gas and you got yourself race fuel

kill two birds with one stone