which lights stay on. if it's the lights in the doors take a look u have switch in it maybe somebody touch it... hope this help sorry for my english i'm a frenchy
i'm not sure if my infos are right... but the ECM on a c4 and the digital dash could be a problem if you want to go far in engine mods but at least for the cat back you'll see a small difference in performance and you'll like the sound of your car. In my case i'll keep the c4 stock and save...
drive it ... don't worry about the others and you can't be responsible for the conditions of the others. I'm sure you work hard for your money and you can spend it the way you want.
this is my 0.02 cents
:D
the cluster if you keep the car i don't see why and i'm not sure if u can't change it with a switch already in it. the only thing you'll have to install it's day lights. the fees to cross is the taxes and if your willing to go at the border and do it by yourself u can save maybe 200.00-500.00$...