My 4x4 is about stage 3 and it's the only car I own so it goes everywhere every day! Is it reliable? Yep, for a Ford. I've only broken down once this week when the fans failed and it overheated, though I did lose reverse gear for a couple of days earlier in the week due to the lift-up linkage thingy breaking. And the indicators stopped working yesterday.

So yep I've had 3 things break this week, but none of them was to do with the car being fast or tuned, just from being a Ford!