The TDI stand for Turbo Diesel Injection or something like that, there are not hp monster but have good amount of torque, like 150lbs of torque, dans the GTI is a sportier version of the car, the body is the same, but the spirit is differrent, and you can have a GTI with a 2liter, with a 1.8liter turbocharged or one with a VR6, depend on your taste and personnel preference, but i suggest you to check the last 2 and please, take them with a manuel tranny, your welcome !