Yes check engine vac again 17 / 18 is a bit low ( not enough vac ) engine vac is a good tool for under standing cylinder fill which cam timing has a big influence on .
Why did I ask was there 4 cam sensors on the engine .....
Let's say the cam sensor was on inlet cam and the cam timing was off by a tooth on that cam ,the ecm could see this and flag ....' Cam to crank correlation codes
But what if the exhaust cam was off and that did not have a cam sensor .....the ecm would never know this but the issue could be seen by missfire detection or lamdas as the cylinder would not burn as well which will leave higher oxygen levels because of poor burn
4 gas reading before cats is a good diagnosis tool also as cam timing being off will make more hydrocarbons ( un burned fuel ) the cats are good at masking this that's why testing before cats is key , but obviously you need a gas analyser for this .
Let's just re try that vac test and see what we have .
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