I recently had my top half replaced, on Mazda's dollar due to a known issue wither the 2004's having a carbon build up and killing compression, this was about 4-5 months ago. Shortly after that my "low oil" light would come on and turn off. Never low on oil but the dealer said it was the float sticking. Now my light doesn't come on but my ptessure gauge drops to no pressure at an idle or while I'm driving, but jumps back up to just over the midrange mark. Any ideas why and how much it will cost to fix?