Jamie,
A lot of the FRS have reported this type of problem It could have spmething to do with the ECU map if you have got the "AE or the AF map on the ECU. as for your Dealer he will not want to work on the car because of the Bluefin more than the De-cat. The Jury is still out on the Bluefin as some have said that this will have a adverse affect on the Car Long term. Hope that helps.