Might I offer a little hard-earned advice??
Have buggered around putting in large engines and tuning up little ones most of my adult life. There is no cheap horsepower gains available, ever. In a V6 you have smooth tractable reliable unstressed horsepower, the ONLY way to gain big horsepower from one, ASSUMING you have an almost perfect low mileage sound engine to start with is:
a) add 3.0 cams as previously told, and gain 20+ extra
b) fit a free flow exhaust, de-catted, and with a larger bore
c) fit a better form of breathing, i.e. induction kit, polished or bigger throttle bodies and smooth all sharp surfaces into the plenum area
d) Have a manual gearbox if you already have an auto to maximize gear ratios and use the available power
e) fit a LSD (limited slip differential) to get the power to the tarmac
f) fit wider profile tyres on different wheels
and.......
If money is no problem-
g)supercharging is relatively easy, but costs mega
h)turbocharging is better, but the same+ mega
i) NOS (nitrous oxide) injection, short term big fix, but relies on a perfect engine to start with, and has reliability issues if used a lot, and NOS refills are stupidly expensive for what they are.
LASTLY.......all this will reduce your fuel consumption to maybe 9 or 11 to the gallon if done properly and safely.
Can you afford to run a car tuned to the hilt that will be a bit of a rough runner inslow traffic, and then you will have to tell your insurance everything and pay them a fortune???
Just a thought or two..........
Mike.