hi im going to be fitting a boost gauge just need to no witch pipe to use to get boost reading please help me pics if possable

i have the octy mk1 1.8 20vt

Search is your friend. Been covered loads of times.

The best one (oddly enough) is the pipe that goes into the top of the fuel pressure regulator. You need to cut the pipe, fit a T-piece in it, and then the pipe off of the T goes to the boost gauge.

Pic here (courtesy of Rob Clubley)

better to get a new bit of pipe insteads of cutting the pipe, then it is easier to put back to standard if you decide to sell it.