A few questions mk4 1.8t AUM

[novadragon007]

was gonna tackle my pre cat lambda today but have a few questions before i go ahead with it.

1. Far as i can tell its a 22mm wrench/o2 sensor socket for the sensor itself can anyone can confirm that?

2. Can i get to it from the driver side wheel well with the shroud off or does it need to be tackled from underneath?

3. What is the size of the nut that holds the pancake pipe on as mine has come off and is hanging loose (hence wanting to do the lambda from the wheel well cause ill be there anyway)

Muchos Gracias

[novadragon007]

nevermind managed to find them all after a few hours on google 

Next question is im gonna test for boost/vac leaks so ive got myself a tester from the states ( i know i couldve made one but i simply didnt have the time and wanted a quality one) its the kind that clamps into the air intake after the maf with a pressure guage and a tyre valve on it my question however is ive seen many different ways to do this and wondering which way is best. The guide ive got with the tester says to plug up the connection on the intake pipe where the "hockey puck" connects to but doesnt mention about clamping the line ive just disconnected so surely all the air im forcing in would just come out of that line. Ive also seen some where the user didnt remove the oil cap or lift the dipstick and the guide ive got doesnt mention it either so can someone help as to what is the best way to leak test the car?

sorry for the noob questions