There's no difference between absolute and relative "boost." If your gauge says 15 psi, presuming it's accurate, than your manifold is getting atmo+15 psi. I think what you're really asking is, does your MAP sensor read absolute (atmo+boost in bar) or relative (just boost). Everything I've read indicates you always want to read absolute, so I would expect the AP tune to be doing so.
		 
		
		
		
		
		
		
			
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