Yup MAF is worth changing and as Ghostrider said its pretty easy...
You will definitely notice a coil in idle but the motor usually gets very rough and jerky if a coil begins to misfire at higher RPM's...
The MAF shouldnt cost more than 200-250 Euro's... Here's a DIY article from Pelican
Pelican Technical Article: Troubleshooting and Replacing the Boxster Mass Air Flow Sensor (MAF) - 986 / 987
I sure hope this helps... and i will see if i can find an article on the Coils as well
Heiko