[BHP231]

1987 Euro spec car in Australia.
My boost gauge stopped working ages ago so I plumbed in a new after market one with a vacuum line above the KLR in to the new gauge on a bracket below the radio location.
In a moment of boredom today I pulled the dash out, gave it a clean up, pulled the boost needle off and put it back on and after putting back together the gauge works!

Question, dash boost gauge reads about 1.75 bar under load (I read that it is the correct stock level), aftermarket boost gauge reads 10psi at the same time. Obviously one is wrong… car pulls strongly under acceleration.
I was going to pull the wastegate and shim (as per Clark’s Garage), should I shim the wastegate or not? Thoughts and opinions?
Thanks