high temperatures

So, I bought a Piper PA-28-181 with an overhauled (complete) Lycoming O360-A4M back in December. The engine now has about 175 hours. I installed a JPI EDM 830 engine monitor back in June and I (and my local A&P) are perplexed by the indications. My CHTs rocket up to 360-370 just on taxi (mixture...