i own the thundercat 31 there have been a few isues with them leaky fuel tanks for starters the tiger drive starting system have also been an isue for some when i recived mine i had to deal with a leaking fuel tank was an easy fix removed a little flash off the fuel barb had to replace the one way bearing in the starter this summer these have been the only isues i have encountered with about seven to ten gallons of fuel through the engine and its still going strong as far as cat vs deep v that usuallly comes down to personal preference i own bolth v and cats and they all preform well if you check the sites for what you are looking for you will hear praise and hatred for each with a little work they will all be a good and enjoyable