If you need something to read knock or literally anything else, you can pick up a Scan Gauge II on advance auto's website for 127 dollars after tax and shipping and get 25 dollars off of your next purchase of $50
Buy ScanGauge II Digital Trip Monitor SG2 at Advance Auto Parts
use promo codes MAC4 and TRT41 in that order (hit apply code and then enter in second code and hit apply code - don't hit enter- )
hope this helps somebody