So I've recently got myself a full custom system from SpeedFab, header to backbox. One thing I've found strange is that even though the header is decat, the eml light hasnt come on (No o2 spacers were installed). In addition, the exhaust fumes seem to smell of fuel alot more than usual decat cars and the fuel efficiency is terrible! not that I expect it to be super eco but I can barely get 150miles to the tank regardless whether I do city or motorway driving. Any ideas?