Dave,

Age old question and you'll get a wide array of responses.

Personally I'd only run as you say, a max of 330bhp through them.

Although, if new pistons in good health then, people like Stu can use clever mapping and there's nothing to stop you running 400bhp (with the RIGHT set up)

Personally, I'd lower your comp ratio on anything above 330bhp but again only for safety reasons and my personal opinion.

There's a post on the main board a few days back about this, might be worth taking a look