Hey,
Yes. I have a WERKS GT engine and stock they are very good! Getting it modified will improve it in any area you would like it to be improved but it may well come at a cost to another area (Or power range). In stock, they are good and smooth through the rev' band with a very good top end power and very decent high revving.

The thing is. You can mod an engine to have an insanely high power, but the usable rev' range will be so small and outside of that range, it could well be a dog. Also. It may not make very good time either. (Fuel consumption could be very high)
Most reputable engine tuners like to have your engine new if you would like it moded. They may also ask what you want from them..... what kind of improvement.
Also. To state the obvious. It come's at a wallet cost too.
If you are thinking of doing it yourself ....... then try to bear in mind they are already optimized prity well. Cleaning port's, blue printing and port matching, ok. If you do, and I do not know what experience you have had doing this work but I would leave the angle of the ports alone and keep the angle's as you find them. New piston and sleeve are around $150 and a crank about $75 So you if you mess up you can always start a new.
I hope this help's in some way. Good luck sir.

Regards
BM