The people that know are the machine shops working on the heads, they are not on DIY forums. If you don't trust your "head guy," who should know more than anyone on a DIY forum, then look for a different one.

__________________
1988 325is (purchased new) sold
2004 X5 3.0 2005 X3 2.5
2008 X5 3.0 (new to me)