I had my master and slave cylinder replaced over last week, and when i got the car back after i let it warm up, i gave it a 2nd to 3rd pull and it seemed to resitate and then go resitate then go. When i took the car to the shop my boost gauge said my vac was 15. and now its at 20.? And my clutch pedal is out of alighment.

 

Does it idle fine? Start simple-check your vacuum lines, check your brake boost vacuum line fitting for cracks and make sure its sealing.

 

This is where i would start, plus a boost leak test.