i have the "small" xe224/230. with a stock convertor it SUCKED. the car was very bogged down until 3000rpm. the car would surge when at a stop light.
now with my 2800 stall it drives much better, it did not decrease my gas mileage noticeably.

not being able to get tracion, should not be considered when doing a mod, just get a set of drag radials and you will be fine.

i highly recommend getting a convertor.

jesse