7 or 8 years ago, I had this weird vacuum issue, seems like no one else had experienced it before. Out of curiosity, wanted to see if anyone has any idea of what I'm talking about, or if my uncle did some absolutely batshit crazy stuff that no one's ever done.

Before I was into professional mechanics, I had asked on several subs, checked CRSX, etc. All suggested IACV or Throttle Body as the issue... as well as motor mounts, things of that nature.

I would idle for maybe 3-4 minutes at a bad red light, and I would see my rpm's rise up to about 1100... that's when I knew it was going to be all fucky. Upon driving, the RPMs would drop super fast between shifts, was a pain in the ass to rev match, and when letting off the gas and coasting it would buck/jerk pretty hard, even when shifting from 2-3, 3-4, etc. RPM's would also hang really bad when kicking into neutral. Dealt with this shit for about a year or so, because, like I said, it was only happening with excessive idling.

Turns out, it was a weird vacuum issue that my uncle caused when he was helping me with my car back around 2017 or 18. I don't know what he did, but all he said was "I spliced them together because it didn't look right". No further information. My uncle has rebuilt cars (1970's though), and was a lifelong engineer so I figured he was not responsible for that issue.

Summer 2019(?), I sucked up a bunch of water on my way to work with my CAI and had it towed to this backwoods guy's "shop" so they could shoot the water out of the cylinders. He noticed the weird behavior while he was letting it run for a bit afterwards, looked at the vac lines, and fixed it. He said "the last person who touched this did some dumb ass shit to it", and I guess fixed it. On horrific terms with my uncle at the moment due to his treatment of a dying family member, and even if I did ask him I highly doubt he would remember. But DAMN am I curious to see what he did. It was something regarding that vacuum port on the intake manifold by the throttle body and cylinder 4.

Never had that issue again, still haven't found anyone who knows what I'm talking about.

So, 7 years later, figured I'd ask to see if anyone else has ever seen this.