It's been over 25 years since I have done any powder coating. You are looking at cure temperatures of 350-400 degrees. I coated carbs sometimes, and don't recall any problems with warpage. If you want to be absolutely certain not to have warpage, just use a UV curable powder. That stuff was not an option when I was in the business. Maybe Lonegunman will chime in. He has current powder coating experience.