No need to buy second hand when you can get the 90a v2.1 brand new for under £55. I've got one on my 7.5 and it runs fine even with boost
http://www.rccarshop.co.uk/index.php...-90a-blue.html
A guy at silverstone bought one of these to replace a brand new revention pro that was faulty, dropped it in with an 8.5 and even though it had the mod software on we added 50% boost and turbo and it was very fast and smooth. Nice and cool at the end of a run too!