Testing through the ICP
sensor requires closing the IPR
valve. There are several ways to do it, but you need to either "backprobe" a PCM
connector or rig up a connector for your IPR
valve that can supply 12V (pos and neg) to the valve.
To do the air test, you get a better test if you listen for the leaks with the valve covers off (for injector leaks), but you also need to listen for the air leaks at the oil fill tube, turbo oil drain tube, the CCV
opening, and at the oil filter housing (filter removed).
The dummy plugs and standpipes are known leak points. They are under the valve covers (in the oil rails).
STC fitting is harder to upgrade.
Simple searches will reveal videos on doing all of this.
The problem is that you need some tools and mechanical experience to do this work. If you can't do the work, then you will probably be at the mercy of a shop treating you honestly. Most do, but some don't. If a shop tells you that you need an HPOP
, then I start to get suspicious. The 05-07 HPOP's are fairly reliable and changing them out when they don't need to be is far too common.