What I mean is the cylinder head on the TTA motor is more commonly used on front wheel drive sedans that are not very often modified for performance. As a result of few car owners of FWD sedans removing this particular cylinder head to port them, there are not many machinists that port and polish this particular cylinder head. This is in contrast to say a small block chevy cylinder head that has been ported and polished by many machinists and the tips and tricks have all been documented. This is all my personal speculation.