idling high 2k, 5sfe mt Options

[ILoveMySilly97]

The idle is fine all the time except when i drive it over 2k rpm. Then when i press clutch the rpm goes down to 2k and idles. The only way i can get it to normal again is to rev up to 2500rpm. Then it drops to 800. I'm thinking the diaphragm might be bad? This happens once in a while. One day it happens next day it'll be fine. A week later it does it again it sometimes a couple days later. Please don't say to clean tb.

1997 ST204
5SFE @ 212k miles
S54
2.75" CAI
2.25" catback-decatted

[VavAlephVav]

I thought I had mine figured out after I cleaned the idle speed control valve and calibrated the throttle position sensor, but a week later its acting funny again it just wants to idle anywhere from 1200 to 1700 unless I give the throttle a little bump then it comes back down.
does it sometimes, and sometimes not. I wonder if maybe the cts is bad. the iscv is clean, and the valve turns freely and the coil ohms out like it should and its air-tight. unless maybe you can adjust that bi-metal spring on the back of the iscv