Power FC, Verso, Link, all cheaper options than Autronic and Motec. Whilst it is best to have your car tuned after such mods, if you drive within reasonable limits, your car shouldn't come to much harm, however, things can still happen.
It seems that GC8's are a lot more mod friendly without tune than the newer models. But always better to get the tune done ASAP.

Hope that helps.

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345hp @ 1.4bar