Hello.
Its possible to put coilovers on Astra GTC J whit Flexride and reset advice on Dashboard?
I'd of thought so, but I've not looked into the flexride side of things, not a had a car in that's had it.
You can purchase coilovers for flexride, they have an error cancelling kit with them. I believe you can purchase the error cancelling kit seperately, the coilovers and kit are KW if my memory serves me correctly.