I've had two Gdi Plus 4's. Although I wouldn't describe it as a flat spot, the power delivery is not linear and combined with the fly by wire throttle tends to be rather all or nothing, made worse if you are new to them. I think you need first to establish if it indeed has a fault or not, did you drive one before you bought as if so how did it compare? Not sure when you live but maybe there is a possibility you can drive another to see how it feels, it may just be the same.
No harm done if you take it briefly over 4000 and you will find it takes off and is a totally different car at that rev range and as others have said, does get better as the miles mount up.
Misty gauges I live with, they certainly don't spoil the enjoyment of the car enough for a complaint, too many good things going on to worry about it!
Hope you get to enjoy the car whatever the cause.
