Nicotine hinders gains is what I have always heard, but if you are anabolics it should not matter too much... I would worry more about Mouth Cancer. But I quit Dipping after hearing that rumour that nicotine hinders gains... might have been off Bodybuildingforyou.com.... let me find the post
it also raises metabolism significantly, so perhaps this is the reason behind hindering gains, any time you a burning off calories, it's taking away.. which people do anyone when they use things such as ephedrine...