You can do it either hot or cold. The thing your are looking for is differences between each side. If one is noticably lower than the other you have a problem. I checked mine cold with 300 miles on it and i was getting 1about 148 on both. Keep in mind the 1000 has some type of a compression relief through the APV valve so that the engine rolls over easier when starting. So your guage reading is actually less than what you really have.
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