My car is having a strange issue while tuning on a dyno. The power curves go smoothly all the way to 6800 RPM then it sudden drop and lost at least 40 hp before slowly gain a little back. Below are my tuner description of the issue, things that we had done in hope to find the culprit, and my car setup. Please help by let me know your suggestion. I hope some of you may had similar issue resolve so I can get your experience in order to diagnosis mine. Thank you in advance.

Here is the summary description of the issue from my tuner:

"on the first dyno run the power dropped about 40whp at 6800rpm sharply then rose slightly as it approached redline. I felt the engine have a odd harmonic vibration at this point also. AFR was good at 10.9 to 1 and the vehicle logged zero knock counts during this. Spark plugs were removed and checked. Spark plug holes 2 and 4 were filled with dirty motor oil to the point where you couldn't see the top of the plug and the coils were soaked. Oil was removed through vacuum and plugs removed for inspection. Gap on plugs was .28 which possibly could have been causing the seeming misfire. At this time new Iridium plugs were installed. and coilpacks swapped out with others. Another dyno run was made and the exact same behavior was present only this time spool up was slightly slower and the power loss was more dramatic at the same upper rpm. Still no knock and sufficient ignition timing is present to let the engine properly rev at that rpm."

Things that we did prior to the tune and for diagnosing the issue:
-installed brand new injectors (PTE 1200cc)
-installed 3-port ecu boost.
-installed new plugs.
-different coil packs.
-Compression tested, result normal.
-Checked turbo ok (the shop used a little camcorder to view inside the turbo turbine).

My setup is:
HKS GT-II turbo
HSK 274/278 with Manley valve springs
Full exhaust
AMS IC, Injen LICP
AEM intake
APS bv
Walbro
PTE 1200
3-port solenoid

Head was rebuild last August.

Thanks again.

 

bump for help. Some ideas that I can think of that may causing the issue are:
1. NLTS. I read from a thread that someone here also had the similar issue and turned out to be an issue with NLTS.
2. Cam Sensor. Some of the threads with similar issue are resolved by changing the cam sensor.

My car is in the shop and they're closed now. I'll try to verify these two possibilities next week when they're open. But any help or suggestion will be appreciated. Thanks.