I had a rebuild from a very reputable builder less that 1500 miles ago. Im not sure if im just now noticing it or if its always been there, but I feel like I am hearing a noise I didn't use to hear. Above 6000 RPM im hearing what sounds like a vacuum with along with the noise of the engine. I had rotor housings, irons, all oil scraper rings, apex seals, etc replaced. Really the only thing that wasn't replaced was the E-shaft and the rotors. I also have a separate issue where the new transmission I purchased shifts pretty rough despite replacing fluid at 1000 miles with redline MT. Only thing I can think is perhaps the additional rod from the BHR midpipe I didn't have welded on is causing movement in the midpipe and causing some movement from midpipe/trans to engine. There's been a few times I couldn't really move into reverse without rolling back out of the driveway a bit.

In the video attached, the car is under load traveling at about 70 MPH and I am giving it gas with the clutch engaged running from 5000-8000. Aside from the normal engine sound, if you listen closely, it also sounds like theres some sort of vacuum noise behind the engine noise. I also feel like my performance is slightly less than what it should be above 6000. The performance between 6000 and 9000 is mostly the same. Builder media blasted and cleaned all internal parts to ensure all intakes were carbon free and moving appropriately. The only real change he made to the car was removing the tubing that used to be attached to the airpump that I had capped off. I assume that he pluged it at that source. I am also using 10w40 rotella diesel oil as recommended by the builder and pre-mixing.

It was difficult to actually record the vacuum noise from the cab, it sounds more pronounced in person. Between cabin noise, road noise, and the engine noise its difficult to hear but if you turn the volume up, you should be able to hear it.

Current mods/new parts:
BHR midpipe
Airpump Delete with blockoff plate
foam placed around radiator.
New radiator
new engine + components
new oil cooler hoses and coolant hoses
new transmission


(Video below, cannot figure out how to convert from MP4 to an accepted file type)
https://imgur.com/a/95wuKLd

 

Does it only happen at full throttle, partial throttle or any time you're over 6000 even if off the throttle?

 

Its correlation is with the RPM. If i push the throttle to 9K, the vacuum noise starts and as the RPM drops, its not really noticeable after about 5000 RPM. Do you hear it or am I crazy?