im putting on a new cat-back system on my car. I bought a new convertor to replace the factory one. My question is... Do I need a simulator or some sort of chip for the ECU and o2 sensors? Guys at muffler shops have been telling me i'll need it or my whole ECU will be messed up. Any suggestions on what to do? should i just ignore what they tell me and go ahead with the installation without any chips? HELP!!!