Moved, RM 250 jetting ? for elevation change

I have a 93 RM 250 with an FMF Fatty moto. The bike came from Wyoming at 7,300 feet. It's here in Iowa now (not sure what elevation) and I need to know where to start. The bike would load up some when it was out in Wyoming but now it sputters when you get on it hard. Some of that might be due to the half kinked expansion chamber that I am replacing. I have read all the jetting guides and am lost as to where to start. How do I determine what jets it has in it now? Where do I buy different jets? I've been to JD jetting's website but they dont have anything for that old of a bike listed. Some help would be GREATLY appreciated.

thanks
Josh

would it be easiest to return the carb to stock jetting then go from there?