Should get you an extra few bhp mate, you can get them on ebay, in fact I just sold my last one there! There's an excellent "How Do I..." feature here on the website showing you exactly how to do it, you'll have it off and the new one fitted in 15 minutes.
On a 1.8 VVC with no other mods, you'll gain about 3-4 bhp at the top end, with better (smoother) throttle response.
Plenty of info about fitting on this site - takes about half an hour.
You can often find used 52mm TB's on ebay, if you prefer a new one you can buy one at your local MGR dealer or cheaper online at places like www.mikesatur.co.uk or www.eliseparts.com
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