Trying to decipher the sensation you're describing. Is it related to holding a line (like Koogar mentioned), or does it feel harder to pedal?
The first one can be mitigated with Koogar's tips. The head tilt thing helps too. I've best described it as "leading with your chin". You can also drop your inside elbow to initiate the lean into the banking. These two things I have found to clear up most peoples problems with holding a line in the banks.
The second one is a mental thing. Most people back off their effort in the turns because the G-forces tells their brains to do that on a subconscious level. You can in fact, raise your speed as long as you keep pedaling faster (not harder) when you lean in, because your center of mass (which is already moving at a constant speed) is traveling along a shorter path than your wheels, causing your wheel speed to increase. This comes with practice, but shouldn't take long.
These graphs illustrate that effect
http://photos1.blogger.com/blogger2/...0/PursuitA.jpg
They can even predict it's effect when modeling pursuit strategies
Figure 3 about 80% of the way down the page.
Training and Racing With a Power Meter Journal: May 2010