No inlet tube on your car. That'* an emissions sampling thingie.
Length??? Dunno. Just buy one, and they'll make it fit
Don't waste your munny on a name-brand for a cat. Buy a carsound. Same performance, virtually a straight pipe as far as backpressure is concerned, and alot cheaper. One of the 'big three' makes the carsound, anyway.
Mine was $125US installed. It'* a 3" inlet/outlet, with custom flanges. Wanted to make sure it flowed well, but still did it'* job as far as emissions are concerned.