RPM Surge After WOT, Weird Idle, Worried I’ll damage my engine Options

[drewvw]

Hi All, experiencing a tricky problem and I’m worried I’ll blow the engine if I don’t figure out.

73 1.7, fly cut heads, SSI/aftermarket exhaust, mostly stock otherwise.

Core Symptoms:

- Idle rpm inconsistent. Steady, but it seems to keep changing its mind on whether it’s 400, 1000, 1500. Decides again after you’ve been driving and slowing down for a stoplight or something. Gets a bit better when warm.

- If I floor it, when I change gears the RPMs continue to zoom to redline levels. Can’t say for sure it’s an air leak type of surge, might be sensor or linkage (investigating next) based. Does not seem “floaty” like air if that makes sense, more hard.

I’ve owned the car a long time and it general it runs great. But this has been an issue all summer. Just replaced exhaust and shored up SSI. Pretty Thorough review of vacuum lines, points, sensors, timing, etc. Swapped in another MPS.

Looking for ideas here, tonight was scary with the RPM revs.

Will update as a evaluate more. Thank you are any help!

Drew