is AEM CAI for STI bad?
i just bought it and have it installed yesterday... doesn't feel much different from the stock except the by pass valve noise is now noticable

heard people say CAI will cause the engine run lean, is it true?
how do i tell if it is running lean or not?
what's the impact if the enigne is running lean? how does it do damage?

 

You won't feel a difference. The MAF adjusts for the extra air by adding more fuel. In cars without MAFs it will cause the engine to run lean, increasing power. But, in cars with MAFs it wont do anything. No gain, no harm.

 

you have that backwards
cars (turbo subarus anyway) with maf+ intake = lean (bad)
cars with out maf ie 2000-2004 RS has no maf and are fine

the diamated of the intake and the bend befor the maf cause an inacurate reading

basicly no save your $$