Fuel economy degrading after Tuning

22L/km is like armor vehicle. It is probably heavier than M1A2 Abram or Leopard 2 tank.
Probably you meant 22km/L which is about 4.3L/100 Km or 55 MPG, which is very high. Most people only get 45-50 MPG mix city/highway.
I never recommend cleaning the MAF just because..., it often does more harm than good. I am not sure how do you clean catalytic ocnverter that contains ceramic with Pt,Pd, Ro metals on it. It also often just placebo effects. Unlike Diesel particular filter, there is no sludge or shoot on gasoline car catalytic converter because they are very hot, turn everything to ash.

I think you measure the MPG not accurate enough. You should do a trip at minimum 1 full thank or 600 miles or 1000 km before getting good enough statistics

 

^ That and your probably getting bad diluted petrol.
Whatever caustic chemicals you dipped your Catalytic converter into may have stripped the materials out of it to perform it's designed function - rendering it useless or inoperable.
Spark Plugs should be replaced, not cleaned. It's in the combustion chamber, it'll get dirty again as soon as you start the engine.

 

I actually clean and reinstal the sparkplugs every 5 years/60k miles because the change interval is 10y/120k miles in Denso Iridium SC16HR11. I only clean the tread, nothing else because the tips are in perfect condition. There is no such things called TUNE-UP in modern car. The ECU with injectors, O2 sensors, and MAF works dynamically. We only say change air filter every 4 years if the air is not too dusty. The cabin air filter is the one need to be changed or washed every year. The original Denso or Bosch filter is fiber glass and can be wash with laundry detergent.
If you live in hot climate, make sure turn the AC ALL the Time. It is part of the cooling system for the hybrid battery. Park the car inside the garage to keep everything last longer too.

 

Did you disconnect the negative battery terminal for at least 5 minutes after doing this? This is a good idea because it will force the ECMs to go through all their recalculations and resets so the car could run rough for a bit but, then, will normalize and should bring those mileage numbers back up.

 

That's true if one clean the throttle body, the air mixture may be off and the ECU will do relearning. Removing the 12v battery - pole will reset the ECU throttle opening air mass learning.