I live in NC and have to pass the ob2 as well. Ive got a built aristo gte im going to put into my is300. Like stated above, my tuner told me that all the is300 sensors will have to be used. He likes working with Haltech so he told me to purchase whatever haltech system i wanted and he would have to run it parrallel to the stock ecu. Im pretty sure he actually told me i would have to run the aristo engine to retain vvti to help keep the stock ecu happy with that. Not sure if its nessacary or just something he recommends. Only input I can really give is to talk to local shops in your area that may have experience doing it. There are also a few threads that have the info needed to do it.