Looking for some help if possible.

I recently replaced the MAF, and after a service a few weeks ago (new plugs) my mpg's have reduce severely, currently around 26mpg. This is on a year 2000 2.0L petrol. Mostly doing motorway journeys too. mileage is 86k.

The air filter was a bit dirty so i'll replace that this week at some point. I have no engine management light on.

Noticed that the idle is a little bit rough, seeing a little suit in the exhaust.

Any thoughts?

Cheers