Yeah, don't worry about lag. Turbo sizing is going to be the key to it all. You the customer just tell us what your goals are and we'll recommend a size. If you know exactly what turbo you want then you just tell us and we'll order. Of course if it looks like the choice might cause issues we'll point that out too.
If your power goals are so great that it may end up with some lag or other negative aspect then we'll tell you that too.
Also, having this turbo on at the recommended levels is not necessarily going to go out and break a bunch of stuff. Using this turbo kit on 7psi we sell it at will work fine on a stock transmission and SVT clutch. You might have a lot of wheelspin with the stock diff and you might break the stock diff if you do clutch drops, but you have that in the stock configuration anyway.
The single best mod to this car aside from more power is a LSD with another OEM SVT clutch or a quality replacement clutch.
Spec stage1 comes to mind as a great clutch if everything is machined right AND if you take the time to break in properly.
Figure 3K for the turbo kit, $1000 for the transmission parts + labor and you're home free. Most people could install this turbo kit themselves before they could replace their own Differential, if that tells you how easy it is.
Oh, and if your engine runs well now, then it will probably run about the same with the kit.
The only two problems I'd say would be more of an issue with a turbo kit installed are: COOLING SYSTEM and OILING SYSTEM issues. I don't mean gasket leaks, I mean pressurized oil and coolant.
If you coolant gauge is in the middle all the time, you've got no leaks then you should be fine. Oil system should be fine if you've got no pressure lights.
You also don't need any worn out plugs or wires.