Poor performance issues, no codes

My wife's 2007 Prius seems to be having issues lately. The car seems kind of underpowered, and last few tanks of fuel have been low 30mpg's (was 40-42mpg until recently), and smells gassy for a few minutes on startup. No trouble codes either on Dr Prius, nor on Techstream. <EDIT: C1256 brake actuator and B1421 air conditioning solar sensor(factory bug) > (Though not sure what those two codes would have anything to do with this current issue.) But the traction battery is running hot, around 130 or so, and car is struggling to get to 70mph for even a minute or two. Ambient temperature today was about 90F. A few months ago I overhauled the traction battery, replacing a couple weaker cells with good used ones that I individually refurbed recently. Looking at TS and Dr Prius, the numbers all looked pretty good, except for the 130F temperatures. The cat was replaced about a year ago with a reputable one from Amazon, which so far seems to be keeping the O2 sensors happy. I guess tomorrow I may pull the plugs and inspect, maybe do a compression test, and clean the throttle body. Did an oil change a couple weeks ago. I'll check the air filter as well. Someone suggested checking for vacuum leaks, though I would have thought that would have triggered a trouble code. I'm a fairly experienced mechanic, but most of my training was a long time ago, back in the days of carburetors and points ignition. I do have some experience with fuel injection and engine computers, but the Prius seems a whole different level of complicated! I do have the full factory service manual pdf, but so far haven't found any smoking guns. Suggestions would be welcome!