what kernel are you using? i tried a few kernels, and ended up using p3's 1.0 ghz kernel without any problems...
have you tried setting your profiles in set cpu? there is an "overclocking 101" thread in the forum which gives a very in-depth tutorial on overclocking.
i'm actually on p3's 1.0 kernel as well. so far my phones temp has been over 100F so far averaging at about 103F which is unusually high.
Does it run hot while it's on 3G mode? Try turning on WiFi for the Internet connection while at home and see if it runs any cooler. When you changed over to this ROM, did it modify the baseband version or does it still have the same baseband as before? If it does run a lot cooler on WiFi, then check your dBm level on 3G (Settings>About) and see if the signal is running low (like maybe -92 dBm or lower). Low signal makes the radios run hotter because they have to transmit the farther distances, and if you overclock too, this can send temps over the top. I figured out that when I have lower signal, my phone starts getting hot, so nowadays I try to use it on a local WiFi signal as much as possible so when I am surfing a lot at home, it will be close to the router and get a nice strong signal and thus the radio will use less power to communicate to the AP and thus, the thing stays a lot cooler. It's such a big difference, you can feel how much cooler it runs on WiFi just with your hand holding the phone as you use it. 3G will run cooler too, if you are closer to a tower and your getting -80 dBm or better.
Also, on mine, in SetCPU, I have mine set normally at 1000mHz max speed, but I made several profiles for battery temps so that when the temp initially even gets to 100 degrees, it clocks down to 800mHz, then another rule for when it gets to 111 degrees, it clocks down to 600mHz, then another rule for when it gets to 122 degrees, it clocks down to 400mHz, and finally a last temp rule so if it hits 124 degrees, it will clock down to 125mHz. Since I set these rules though, it never gets that hot anymore (haven't seen it past around 100-102 degrees, before it will cool back down on its own). Before I set those rules, I only had one rule for 122 degrees, and it would sometimes get to 115 degrees before. So now my Profiles in SetCPU are more proactive in keeping the temp under control to begin with, before it has a chance to get out of control.
But there are many factors that can influence the phone's temperature. Battery charge state (i.e. charging on AC, or USB modes), rapid charging, rapid discharging, 3G signal strength, WiFi signal strength, Screen brightness all the way bright can also cause battery to discharge faster making battery hotter, and the backlight LEDs for the screen also create heat, watching Adobe Flash movies that are higher quality tend to be a heat generator for me as well. A few video clips and this thing wants to bake. But like I said, if you set up many temp profiles in SetCPU you can have a more protective, proactive approach to managing and keeping your phone temps under control before they get so high that it is hard to get it back under control.
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