carb spacer
I'd venture to say that due to the size of the engine and smallish ports and lack of a plenum on the eddy performer it might respond best to a open spacer. Just make sure you have the hood clearance for it b4 you buy it. Don't know if Demon has got things sorted out but have heard many times of quality issues with them. I've used a lot of Quick fuel stuff and always had good results. Another option is to buy the Holley main body upgrade kit. You use all your exterior parts from your 600 to convert it to a streamlined 750. Only drawback is the choke is eliminated. The main body kit costs about $130. Lots cheaper than buying a new carb.