im planning on making a custom intake with some k&n filters. but i need to know what size to buy. for example what sixe inlet???

 

2.5" i believe

 

4 inch straight cylindrical with 2.5 inch inlet. Thats the average size that people are using for the twin turbos due to the fitment of having two filters on top of each other. This is what i did using damian's heatshield (sick **** damian! it hella works!) and bomz intake hardpipes. The sizes is what i use and fit perfectly.