the tps is the throttle position sensor

when these f*ck up it makes the splutter and hesitate

my mates old saff had a didgy tps on it and it drove fine on boost, but would idle all over the place and hesitate and splutter when driving slowly at low revs

its really easy to change, its the part by the throttle, cant remeber what colour it is but you cant miss it

http://search.ebay.co.uk/cosworth-throttle_W0QQfltZ9

hope this helps. and it may save a journey