2008 Prius losing while accelerating power. No codes

My 2008 Prius keeps losing power intermittently while accelerating. I'll hit the gas and then maybe a second later after it's started gaining speed it'll stop for a second before going again. It use to only happen once in a while at high speeds (90+) but yesterday it started doing it at normal highway speeds, no codes or dash lights came on. I have a craftsman code reader I keep hooked up to it and used it to check live data while driving. RPMs dropped when it cut out, also watched them get as high as 5k while going around 65mph. Set cruise control to maintain speed at 65 and it stopped cutting out and RPMs returned to normal. When I got home I parked and floored it to see if it would do it just sitting in the driveway and it wouldn't. Driveway test couldn't get RPMs above 2500 but I don't know what's normal for that

I recently replaced the inverter cooling pump with a new aftermarket one. Battery was replaced with a Toyota OEM version about a year ago. When I replaced the coolant pump I took it to a hybrid mechanic to read the codes and do some other things and he said there was codes for the transmission he'd never seen before, all he works on is gen II Priuses and said he'd never seen a transmission go bad and not to worry about it. Could that be it? Help?

Other possibly helpful info:
Car has 275k miles on it.
Engine burns oil like crazy (I'm talking 4qts per 1000 miles. Not leaking, burning)
I just had an oil change two days before.
It was over 100° out, coolant temp read about 200° on my scanner. I usually only drive at night and early morning because of my job and today was the first day I drove it in heat like this.
Car had sat for a week while I was on vacation but I've been driving it for a few days since being back with no issue until now.