I certainly wouldn't pull the head until I had done a leak down test to figure out exactly what the problem was. If you can find a mechanic who's experienced with leakdown tests, use him. However, bear in mind that there are a lot of mechanics who are clueless about this, or worse, they think they know how to do one but don't really.
Here's a link in case you want to do it yourself. http://www.xs11.com/tips/misc/misc3.shtml