2013 Hyundai Genesis 3.8 Track sporadic throttle Rev issue

So I have this problem with my car I’ve taken it to the dealership to have them look at it and they said they couldn’t duplicate the problem. So that was a complete waste of my time. So I’m on a mission to fix it on my own now and hopefully you have a solution for me. I bought a 2013 Genesis 3.8 Track when I’m driving if I hold the clutch in while coastingt my RPMs will raise up they first drop down not all the way but a little bit to about 800 then slowly increase to 2000 then it will drop to a 1000 and slowly increase to 2000 again and again. It sometimes won’t even drop it will just stay at 2000 if I tap the gas like you would do to a carbureted engine to kick the choke off it sometimes will make it more aggressive and the RPM’s will raise higher the highest I’ve seen it get to is 3500 RPM’s. It wasn’t every time at first it would only happen after I drove somewhere turned it off then started it up and drove away then it would happen but it’s happening more often now. If I get on the throttle then use the clutch to coast it will start to do it. If I come to a complete stop my cars RPM’s will drop to the appropriate RMP’s which is 6500. It will stay there with no stutter no noise it’s like nothing is wrong. If it’s in neutral or in gear doesn’t matter which one so long as I’m coasting it will happen. At first I thought maybe the clutch and the throttle were intertwined but after doing research I don’t think that’s the case. Also I tried to buy a book on my car a Haynes or a Chilton manual but I was told my car is to new. That they don’t make them for my car yet. After talking around I heard it could be bad gas well I only use premium from Shell Gas station. Or that my throttle body is dirty. Well I bought throttle body cleaner and removed the throttle body. Cleaning it and put a new air filter in. At first I thought that it worked but still didn’t fix it. I was thinking about buying a new throttle body that maybe something is wrong with it but if it’s not going to fix it then I wasted a bunch of money. They are quite expensive so I would prefer not to go that route. I also seen something posted on a page saying that they had seen an instance where there was a coolant leak and it was flooding out the coolant sensor which gave spurious data, which caused the engine to ask for more fuel. Well I can smell coolant coming from my car after driving it but there hasn’t been a puddle and I bought some antifreeze but haven’t had to add any of it. My car has 51,000 miles on it and when I bought it there was only 43,000 on the odometer. So again it happens only while the car is rolling. If I come to a complete stop the revving stops and the car idles right but only when I come to a complete stop. If I’m even rolling at 5mph the RPM’s will still rise. I could have it in any gear with the clutch in and it will happen or I can put it in neutral and take my foot off the clutch if I’m rolling it will rev up but the minute I come to a complete stop the RPM’s will drop to normal so my car idles normal when stopped. It starts just fine if I rev the car up while stopped the RPM’s will go up and come back down to normal no problems but if I’m coasting is when it happens clutch in or if it’s in neutral. If I put the car in gear there no problems it runs correctly in gear it doesn’t raise up it will be at the correct RPM’s that the car supposed to be at. Your help would be much appreciated I’m running out of ideas thank you.