Have you tried reading the part number off your MAF? (oh its MAF btw before you get parts guys looking at you funny lol)

Did the garage not clear the fault codes after they replaced the Lambda sensor because that will need doing?

To be honest it sounds like the MAF is working otherwise it would drive the same if it was unplugged or not. If its ignition system related I would put money on the coil pack being at fault. How many miles has the car done? The leads may need replacing as they degrade over time.