You told us it's a gas carb with E85 metering blocks.
You told us the guy who put it together didn't like the way it ran and gave it to you. You are a lucky guy!

Simply sell the E85 metering blocks and buy gas metering blocks from vendor of your choice. Or trade. Someone who wants to go E85 might be willing to swap straight across. Look for blocks from a carb the same cfm. Billet blocks are preferred because everything is more precise.

I'm making an assumption here that the guy who gave you the carb didn't mess with things like air bleeds and flow restrictors.

Thumper is a board member and has his own metering blocks made.
He has a very good reputation here and would be more than willing to get your carb set up right. You could ship him the carb for a reconversion. He could check air bleeds, etc.

If I had your problem I would change one thing at a time (unless having an expert pitch in). You are getting some pretty specialized advice here which may be good in the end but I think you need a baseline.

So put down the drill and pick up the telephone! Good Luck!

R.