I have my cable now so hopefully I can find some time later today to hook it up. Going back to my original post though, I think I know what the problem was. The car became noisier and noisier and it became apparant the exhaust was blowing. On inspection, I found that there was a hole in one of the pipes on the cat. I stuck a bit of putty on it as a temporary fix and hey presto, perfect gear changes! It's still a little loud but I can't find any more leaks. I have a new cat and I'll be fitting it tomorrow so I'm hoping the old one is just bunged up and that this is what is causing the noise.