how can I remove OEM air filter box?

Any removal manual?

Whats the diameter of the standard turbo intake pipes?

 

Put one hand on each end of the box, and pull up.

There is no standard diameter. The tube is very convoluted, the diameter varies as it leaves the turbo and comes up to the intake box. If you really want to upgrade your intake, you need to change the intake hoses...9ff, TechArt, and EVOMs all make replacements.

 

It's all right here

 

ya just pull up like everyone said.

i put my BMC filter in this weekend. No real noticeable difference in sound but for a few hundy what did you expect. lol

 

Does the BMC make your engine run leaner without ecu tuning?

 

the ecu will compensate for minor air flow differences no problem.

 

No, it is in closed loop under a certain throttle plate angle the A/F will remain stoich. On stock twins at full throttle it will be in open loop and the additional cfm from the filter if any will not make any difference.