For info in case anyone else was interested. Emailed celtictuning about their experiences with this car and the issue of Alfa overwriting the new software during routine maintenance.
This was the answer :
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The Brera JTDm engine we can take from 200bhp and 295lbft torque up to 250bhp and an impressive 369lbft torque. All our maps are developed using the dyno to ensure correct fuelling for MOT compliance and to ensure it is within tolerance of engine and drive train components. The performance once remapped will be impressive and under normal driving conditions you can expect to see an improvement in fuel economy.
The remap is fully undetectable and comes with 14 day money back guarantee which gives you more time to trial the results on the road and ensure it is what you are after. We also carry out pre and post diagnostic work to ensure all is fine with your car.
The cost of the remap is £425 all inclusive for which we come to your location. In regards to the software question. Alfa should not load a new software flash onto the ecu. However, if they do then we will redo the remap free of charge. We have now done about 25 of these vehicles and each one of them are very impressive.
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Very tempted indeed!