If there is no difference when you unplug the maf you almost certainly need a new one. Second hand sensors are a bit of a false economy, especially with all of the engines they're fitted to being more than 10 years old now lol. Unplugging the maf will have caused a fault code, but it won't light the EML except on the really early cars (T-reg). Everything you have said points to the maf.
You'll know if the cat is blocked as it will struggle to rev even unloaded and you will be heavily down on power. Yet to see one of these with a blocked cat. Open egr, jammed air-doser, etc will cause more power loss higher up the gears (when more air is required/back-pressure produced), not so much in first and second.
You'll know if the cat is blocked as it will struggle to rev even unloaded and you will be heavily down on power. Yet to see one of these with a blocked cat. Open egr, jammed air-doser, etc will cause more power loss higher up the gears (when more air is required/back-pressure produced), not so much in first and second.