07 H6 specB pinging/timing issues

[Joeyims]

Hi all, bit of an issue I have with my H6 auto with 97,000kms. Always used 98ron either bp or caltex.

It's developed a chattering/pinging kind of noise under load, at very specific rpms. At 2500rpm in 2nd or 3rd gear, and 4500rpm at most gears. Mid to heavy acceleration.

There are no CELs, and it doesn't seem to affect performance while the noise is happening.

Had a few different opinions, and a diagnosis from subaru, they reckon the car has too much sludge inside, blocking oil paths and solenoids. Was quoted $10500 for a brand new engine.
I have been flushing and UEC-ing the engine every week now, to try and get most of it out. I did initially notice a bit of improvement, but the noises are still there.
I have the car booked in with All Drive Subaroo next week, but thought I'd get some info from people who had experienced this.

Here is what I do know for a fact:
- Car has erratic timing. Driver side seems to be lagging behind.
- pinging seems evident, although it gets much better once i drop a bottle of octane booster in it.
-does this mostly under heavy load.

Anyone who has experienced this, your insight will be much appreciated. I fear it's one of those things that are much more hassle to fix than they are worth. Read a few threads that have similar symptoms to mine aswell, where the end solution was to drop another engine in.