G14 Runs great when cold but then won't rev up

[jdt162]

I have a Yamaha G14 gas 4 cycle golf cart. When I start the cart (cold) it will run great for about 5-10 minutes. After that, whenever I let off the gas and bring the RPM's down to where the engine shuts off, it doesn't want to rev back it. It turns over, it just won't rev it. If I press the gas pedal very gradually, I can sometimes get it to run again. Once (if) it gets back to full throttle, it runs fine again. I've already replaced the fuel lines and fuel pump but this didn't solve the issue. What baffles me is that it runs great when cold which would lead me to believe the carburetor is fine. It also ran great for the weeks prior to it having this issue so it's not like it was sitting for a while. If I let it sit for a little while, it will run fine again for 5-10 minutes and then the problem returns.
Before I replace the ignition coil, I wanted to see if anyone else had any suggestions. I've read quite a bit on this site for the past 2 years and I appreciate all the help so far. Thanks!