Accuracy of HP gains in products?

[fast 3.4]

This is for a pulley kit from Summit Racing I'm thinking of buying when I get paid...

http://store.summitracing.com/defaul...=egnsearch.asp

"Get up to 15 extra horsepower in 30 minutes!"

I know that a company has something to gain by exaggerating HP increases, but is this true for every company? What's a trustfull, accurate company? Sorry if this is a dumb question, but I'm relatively new to buying parts and I want to get my money's worth. And a lot of times I read people on this and other boards second guessing HP increase claims. So, what's a good rule of thumb? When it says 15, should i think 8-10? And what's the real plausible HP gain from this pulley kit?

Thanks.

[98Camaro3.8]

Accuracy in Ads? Ha!

You might get 5-8 hp out of it. Maybe a tad more, because I know the 3.4s respond pretty good to underdrive pullies.

[fast 3.4]

Well that's good to hear for $54.00. I hear they don't do much for LS1's and LT1's though. Thanks.