Yeah, I know they go to raise compression. Just my porter when I had an 02 silvy with an ls1 and 5.3 heads, ported them and put in bigger valves and said they outflowed a pair of ls1 heads he just grinded on. :shrugs:
It would cause a problem b/c then you cant get your accessories to bolt up. the ones that will, will and if i remember right, its a tensioner that wont mount. I have thought of fabbing up a bracket that mounts to the intake and then also has a mounting point on the side to move it over, so car intake will mount truck accessories. I just havent really played with ls1's in about a yr, been concentrating on my suspension setups. So i'm not 100% if its a tensioner or something else.