I have to send my car (91 TT) to emission pretty soon, but I have taken all of my cat-converters out. Does anyone who has dealed with Random Technology with their aftermarket converter & downpipe before? Or does anyone know if Precat replacement would be enough to pass the emission or Back converters replacement also is needed for emission. can i only replace either Precat or back converters???? Thanks for help!!!!!!!!!!!!!! (Dearler charges a lot!!!!)