Any muffler shop worth there title can build a cat delete, Just tell them to keep the pipes as close to the stock length as possible. This is not a hard job for them!! so stop waiting for some 300.00 delete to happen and save some money also.
don't need it, but you might lose a couple hp up top. depending on a couple variables. I,m at 700 feet above sea level. so since the o2 sensor only works in the lower rpm's. any mods to increase air flow will affect hp more the closer to sea level you are. ( it is tuned for sea level ) the higher your elevation the better the chance of gaining hp up top. since the higher you go the less air you are getting, so intake/exhaust mods work better in higher elevations. since it increases the amount of air you are moving. any one mod and its still close add a couple together and a controller becomes necessary, so you are not running to lean .
Isn't there an airflow meter to alter fuelling ?, along with the other parameters, Which would compensate for any air flow differences.Modern airflow meters can also monitor intake temp, don't know if this is the case for the Mav but I'm sure I've seen a plug entering the big plastic plenum behind the throttle body.
I had put a AF gauge in before I took the cat out so I would know what changes it made, It leaned the idle out to about 15:9 from 14:8 stock. Also in stock form on the top end it was rich at 11: 6 to 11:8, that did not change but I put a tuner in the lean it down to about 12:4 and got the idle back to 15:3, and yes it dose run better with this setup.