Probably a combination of RR making it run rich as hell and crappy old coils/plugs giving a weak spark making it missfire. Replacing the coils might fix it if they are bad but you will still be running too rich, a remap or safc, nistune etc will more than likely fix your issue and if it isn't the issue it is still a great upgrade, more power, better fuel economy etc providing you get someone who knows what they are doing to tune it.
A boost leak will cause issues like this as well though, check all your piping and hose clamps.
If you have an exhaust and pod etc you can easily run over 10psi, I've seen up to 12psi with no boost controller and a free flowing exhaust before.