I have a blow off valve on my car that holds 27psi but i want to change it for another. Will this effect the tune in anywhere?

 

It has the potential to effect the tune if the new valve has a stronger spring. I remember on my IX I changed the stock DV for the Cobb XLE. I swapped them and did a quick pull. On the stock DV I would hit 30psi, well once I swapped it for the Cobb it spiked to 35psi. So yes changing the valve has the potential to alter the tune