As everyone has suggested, makes sure the basics are sorted out first
I would strongly advise that you get it on the dyno and see what the AFR's are like.
Going from my experience with a 'remapped' ecu, it made me think my car had a much bigger turbo than it really did
A simple upgrade of injectors and PowerFC, and a bit of tuning, transformed my car from being very laggy to having very little lag at all
A decent tune makes all the differance!
Check out the overlay on this graph, notice the mid-range gains of optimised AFR's and ignition timing
What is not shown is the old remapped tune would run at about 15/1 AFR's in the mid-range, and little timing due to detonation
Now it runs more timing, with AFR's around 11.5/1
Thats where my 'laggy' feeling was, and it was all in the tune