Originally Posted by mechanicalmoron

If it's dramatic, that's somewhere to check.

Did you just look at the hoses? Spraying carb cleaner around stuff can find huge vacuum leaks, but a smoke test is almost always way better, the only (very rare) exception I've found is some intake manifolds, where there is a long gasket that can suck in under vacuum, but not enough restriction to push the smoke out.

So it didn't do that, then it sat, then it did that, with no work or damage in the meantime? If that's the case, put some happy juice in the gas and drive it.

Throttle body clean and happy with no shaft leak, and stopping in the right place when you set the TPS? MAF clean and happy?

I've never used one of those cool-kid computers, do you have livedata? Is it a real adaptive closed loop system with fuel trims that you can watch?