the air flow in and out has altered but not massively so shouldn't cause you any grief although I do suggest a remap as these cars don't particularly like having things changed without the appropriate map changes!
Make sure you haven't knocked any pipes on your way i.e. caught the lines to the DV, boost solenoid etc as you could have caused a small air leak.
Failing that you might well have just been in a bit too much of a rush to change stuff and bashed the MAF about a bit too much..... Take the MAF out and give it a clean, shove it back in, start the engine and then disconnect the MAF, if the car stalls all is well, if the car continues to run you need a new one