Over Boost question
 

I was driving my car hard last fall and after 1 particular stab of the pedal I noticed my tell tale boost gauge showed 1.5 bar boost. My TIAL waste gate has a .9 bar spring and every other time has never passed .9 on the gauge. What would cause the gauge to spike up to 1.5 bar? It didn't feel any faster than normal so I don't think it really did hit 1.5bar, should I be concerned of about this? Do these gauges do funny things sometimes.

Sometimes the turbo will spool up faster than the WG can bleed off and you will see a boost spike for a split second. I have seen this with some of my other cars.

I'm surprised you didn't trigger your overboost switch, my guess is that your boost gauge needs to be rebuilt - mine does the same where the telltale will show max boost (.09 in your case). The on the next boost cycle will drag when the needle comes up again where the telltale shows an overboost. Try to keep an eye on the actual boost needle on your next drive, and be sure your overboost switch is hooked up and in working order.

Where is your boost Gage plumbed?
If before the throttle then you will see a spike when the throttle slaps shut between shifts. The BOV does not react faster than the signal it needs to open the recirculation valve. If plumbed below the throttle you will not see this boost spike, which is good cause that's what your engine is seeing as well.

My car has a factory speedo with boost gauge in the bottom which is plumbed into the stock location. Plus there is a separate boost gauge that the previous owner told me was plumbed into the intake, I thought. This is the one that showed 1.5 bar the one time.