no CEL
safe
worth putting on if u like the sound compensating a very very minor weirdness after shifting
but it doesn't hurt the car at all

 

if u can get the GFB stealth, then u will eliminate 95% of the flutter noise
and u can adjust the volume

blitz is super loud tho
very nice
u feel the air blasting on the ground and u get that DTS ES 6.1 surround air flushing sound

for GFB, it's just [)(] dolby