1. Any codes?
2. How do fuel trims and 02 sensor readings look?
3. How do low and high pressure fuel readings look?
4. Some additional quirks with the engines that might guide you:
The low tension piston rings had a recall so you might see that with a compression or leakdown test.
When you changed the timing kit, did you get a kit matched to your
VIN? There were a lot of small variations to the 2.4 so some people install the wrong kit. Did you replace all the guides, the main tensioner, the sprayer, the sprockets?
I can't remember if the timing is done at TDC exhaust or
intake stroke...the manual tells you. Enough people make that error and engine runs terribly or not at all.
I thought there were a few cases of the cam reluctor slipping. Compare your scope readings to a known good waveforms.
For the spark plugs I know there are some defective ones online. So get them at the dealer or a good local distributor with a serious supply chain.
I would only use OEM coils too. These engines are sensitive.
The PCV orifice cleaning might not be sufficient. In the plastic manifold there are also 4 paths to the cylinders that can get blocked. Removing the
intake is the easiest way to test the 4 paths and clean. I have seen other ways to inspect those 4 paths but don't know how reliable they are.
Another issue with these engines is the high pressure fuel pump. You can see the performance on a good
scanner tool. The HPFP tends to leak fuel into the oil. Sometimes a code pops up; sometimes you can smell a lot of fuel in the oil or via fuel trims with no code. The cam follower which "moves" the HPFP can break too so that should be replaced along with the metal line when doing the pump.
The fuel pressure sensors can cause issues too (both high and low). I think they should throw a code (or at least the pressures should look odd on your
scanner tool.
Finally, the "accessory" belt and tensioner were upgraded. Make sure to change the tensioner. I don't think this would cause your running issues but do it once you get the car running.
