I would be very sceptical about modifications' extra power claims in general. What I learnt when I used to play around with such things, is that between the 'xx bhp extra power' from the free-flow exhaust, and the various claims made about camshafts, air filters, polished heads etc, I should have doubled my engines bhp but this was far from it...
More specifically, I have some experience with cams (though not on the V6), and it goes like this:
1. Some cars have very good cams to begin with, so it is difficult to gain any substaintial improvement with 'fast road' aftermarket cams!
2. Cams don't make power out of nothing, there is usually a trade-off between low-end power/torque and high-end power - with a manual car used for racing you want the 'rally/racing' profile cam which goes into 7-8k and gives extra power, you don't care about low-rpm (sub-5k) at all. There is a distinct point with rally/racing cams when the engine 'comes-on' the cam, which can be at around 3.5-4.5k rpm, a bit like the turbo boost on a blown engine...
3. Cams which make a significant high-end gain, will also suffer from very erratic idle. On one rally/racing cam I used, it was impossible to get the engine idling without stalling unless the idle was set to 1,500 rpm. This was an extreme example though, in most cases you would just get very bad idle - feels like not all the cylinders are firing - but the engine will still run.
4. The holly grail of cams is the one that does not affect idling, and improves both torque as well as power through-out the rev-range, and allows the engine to go upward of the 7k before power peaks. However, as said before, you can only achieve this if the original OE design is not particularly briliant. If the engine has good cams to begin with, the only way to get some gain is by trading-off idling and/or low-end power/torque.
Now I don't know specifically that the V6 cams are of poor general design, but as said if they are good then it will be difficult to get an overall improvements.
Also, when using high-lift cams, you should also consider using upgraded heavy-duty lifters and followers - but in the very list renew all hydraulic lifters as a matter of course as the high lift cams are very demanding on the lifters, any 'tired' lifters can cause the valves to 'float' and burn.
And last, my experience was with Kent Cams (though collegues used Piper Cams at the time), and it was 15 years ago....