Having sailed in the SF Bay for around 10 years now, I cannot imagine a 140% would help with the winds we normally see (although they have been light this year). I find when the wind hit 15kn, with a 100% jib, I am overpowered. If I am alone, I reef; if I am racing, I depower the main just shy of luffing.
As the winds nears 20kn, I move to my 90% jib. Makes things easier to handle. The P323 is a very headsail driven boat; in fact, in heavier wind I have had pleasant sailing under jib alone! DOn't knock it until you have tried it :-)
As Ed (Dolce) said, the 323 like to "stand up" - with such a shallow keel, if you heel to much you tend to end up with a lot of leeway.
Is it possible you are overtrimmed? I tend to find my boat sails better with the sails a bit "fat". People from racing boats often overtrim, slowing the boat down and creating more heel and weatherhelm than necessary.When Selene was new (to me), I often had weatherhelm, and most of it was caused by - and resolved through - the sail trim.
Hopefully some of these ideas help. Good luck!