1993 Toyota Camry 3.0L V6 (five-speed) throttle issue

1993 Toyota Camry 3.0L V6 (five-speed) throttle issue

I'm having an issue with the throttle on my 1993 3.0L V6 five-speed Toyota Camry. It idles rather low (about 600-800RPM) and it shakes a fair bit when it's running low. When I accelerate (even within one gear), the car sometimes shudders and shakes and the RPM goes pretty low. This issue is somewhat inconsistent, usually worst about 5-15 minutes after starting it, but it comes and goes afterwards, too. I don't think this is a problem with my use of the clutch, as I've been driving this car for the past eight months and this issue has only been happening in the last month or two.

I've tried cleaning the throttle body (as in your video). I cleaned it twice. The first time it seemed to help the RPM for a day or so, but then the problem came back. The second time, it helped for all of an hour, and then the issue was as before. I've taken it to a shop, and they thought it was a misfire, so they replaced all the sparkplugs. That didn't work.

Any thoughts?

check for vacuum leaks, and have the fuel injectors pressure cleaned by a pro if not that.