T.31 needs part K&N 33-2944.

Toys4cars have them in stock and my local Halfords said they could order if required. Cost just under £50.

http://www.toys4cars.co.uk/index.php?ma ... et=_parent

In the past I have fitted K&N panel filters and also induction units to various cars. Induction units make a difference but getting a cold air supply to them is vital - no good collecting hot air from the engine bay. I have never found a truley noticable difference with the K&N panel filters against a good clean OEM filter. If anything, getting a better air flow to the existing panel filter may achieve more than changing the filter as the ducting flattens out at the end restricting air flow - how good can that be?
I don't know if anyone else finds this, but when I have given the car a very good clean both inside and out, the car seems to run better! This is because you like it again, it makes you feel good so you tend to drive it with more enthusiasm and you think it's running better. Therefore, a cheap and effective way to "gain increased power with better pick up and acceleration" is to keep you car clean - sorted! I'm not a canny Scot for nothing.

I have to agree with the above..it's like when you pick it up from a service, it always 'feels' better driving it home