Advice needed please (low idle & hesitating throttle)

[Rattlesnake]

Hi all,
I have owned my 2000 year Yaris VVTI 1.0L for 14, years and absolutely love it. Its been insanely reliable and I have always fully serviced it (filters, plugs, belts etc).
In the last year its developed what I can describe as the below:
1) hesitating / very light spluttering when at idle and trying to pull away. I have to tap the accelerator pedal before I pull away to lift the RPM a bit and then pull off
Something interesting is if I put my foot on the accelerator to rev the car high, the first split second from idle it completely hesitates and splutters. The car idles very low (to the point where on the digital dash display it doesn't show any small lines at the RPM garage (maybe ids at 500rpm..?). I think this low idle has caused a whistle noise from the throttle body area.
2) no warning lights at all and no fault codes
3) I've smoke tested the vacuum system and there are no leaks at all, was kind of hoping it would be a simple pipe leak.
4) I cleaned the throttle body and air mass meter. No change

Genuineky don't know what else to check or change, the spluttering worries me as I feel its causing the engine to work harder.

Any advice will be greatly appreciated, I have searched the forum and the below was the only similar I could find but no real answers in it
https://www.yarisworld.com/forums/sh...ad.php?t=56269

thanks in advance!