by the 2.5 block, does it not have to be bore out to make it 3? or do u mean putting a 3 litter pistons in which has a longer stoke possibilly otherwise I don't understand how 2.5 can be converted to 3 without a longer stroke or bore out.
if the latter is the case, does that mean m3 has the same block as 325 but longer stroke pistons ?
i did not quite understood the acronym HG, what do u mean ?
by free flow exhaust i assume u mean a de cat and tail pipe