I hate doing this type of post, apologies in advance, but nothing about this is making sense to me so I will detail everything I have done and tried so far. Freshly rebuilt 13B. Literally hit 1,000 miles the day it happened. Drive home from work completely fine but I notice a slight whirring noise and don't think anything of it, car appears to be running great. Go to take it out hours later and it starts and runs(not well) it sounds like there is a massive vacuum leak/whirring noise near the front rotor housing. AFR is dead lean and getting a ton of backfires. Will not stay running unless I hold the throttle almost wide open. I purchased a rotary compression tester and all my numbers come back good(between 100-120) so there should be no problem with it being blown up. I took off literally every vacuum line and plugged holes to rule out those, still get the massive whirring noise. Remove intake to double check things over, nothing. Took off belts from all accessories to rule out a whirring there and it still does it. Even smoke tested the thing to find a leak and nothing has showed up. I am completely baffled as to what is going on with this car right now. It sounds like its coming from the spark plug side of the front rotor housing near the CAS/alternator area. I know its not the alternator acting up since I removed the belts. At this point I have no clue as to what is goin on and could use some input on what to check. Could it be the CAS acting up on me??

 

Good job on trouble shooting everything yourself so far very thoroughly.

I think a video would really help forum members see/hear your problem. I mean, it is 2021. And some pictures of the engine bay.

You mentioned it could be the CAS. Could you just borrow a CAS from another car and try it? I see there are 2 fc’s in your picture.

 

Will try to get a video later today. It's a 2 person job the way it is running. The other FC isn't mine so unfortunately that option is out for now

 

Try new spark plugs?