Checked for intake leak using propane method on my 2000XK8 and didn't find any. How can I check the MAFS?

 

You only have a Po171 (“A” bank lean) and not a P0174 with it tells me that your problem is on one side and not both. For that reason I would rule out anything that is related to both sides I would focus on poor fuel presentation suggesting fuel injectors on “A“ bank. Get yourself a bottle of BG44K and add it to a full tank of gas and drive the car. You can get this at most dealerships and most good repair shops. Once you use it you will understand why I only recommend it.

Link http://www.jagrepair.com/images/Auto...7_ECM_2000.pdf