Thanks for all the replies, it's good to hear first hand of people's experiences good or bad.

The cars running stage 3+ bluefin so I don't think it's that as it is quite a well known and widely used map.

I'm just looking for a decent garage who know there stuff and don't take a strop when I don't want to pay mega bucks for there time that's all. I was thinking around the £300 pound mark for a diagnosis is this resanoble or am i way off the mark?

I'm a bus mechanic to trade so I've never really used a garage as I have only bought bolt on mods and have been Able to fit them myself but I've got limited knowledge when it comes to the tuning side of it so that's why I would like someone who knows a what there doing to have a look at it