Spiced MSP
Member
- :
- 2016 Peterbilt 579
bad injector seal maybe, if air is leaking through the seal, it can cause a "lean misfire" and could also lower your vac reading since it is a vac leak. Spray some carb cleaner around that injector seal and see if the idle changes. I just went through this after changing to the 505 intake manifold. Only difference is mine was a random misfire due to all the seals needing to be swapped out.