Like many, I have been oogling over the SMY Cluster for the 2008+ Imprezas. I decided to pull the trigger and buy the setup. The gauges were the killer as Defi is not cheap! But I decided I wanted the best so I ordered them.
I must note, the SMY cluster is a fantastic piece of work. The fitment was great and the finish was even better!
I chose the oil pressure gauge and the boost gauge. The flavor was Defi Red Racer Series.
For the oil pressure unit you have to remove the alternator. To be honest it was cake in this car. When you remove the alternator you can see exactly where the stock unit sits and what you have to remove.
Based on XLuben's thread I grabbed a 24mm deep socket and removed the stock sensor and bung: