Have not had issues with either rough idle or cleaning the TB. It's pretty straightforward taking off the intake hose and cleaning, no different than other TBs I've cleaned in the past...

 

I did this summer:

https://www.toyotanation.com/threads/what-did-you-do-to-your-12th-gen-corolla-today.1633354/page-154?post_id=14986257#post-14986257

 

I also clean the gasket screen behind throttle valve which collects carbon as well... Easier by removing the throttle body which allows a more thorough cleaning on the back of throttle plate and throttle body outlet.

 

How many miles were on your hatch when you started to service everything like throttle body?

 

Those who cleaned their throttle body around the 40k mark was it really really dirty as in would you do it again at that milage?

 

Clean it thoroughly at exactly 40k, then document your findings and results... The easier way is to just get in there and do it. It's a very fun and rewarding job.

 

Just did mine last week @ 125,500km or roughly 78,000miles for the First time and it was not dirty at all, but I did because I also developed a rough idle/ hiccups upon startup and a stumbling low idle when coming to a stop . Turns out my original Toyota battery needed replacing…

But anyway, Honestly the amount of time spent asking these questions you could have had it cleaned and found out for your self by now. It’s very easy to do.. Depending on where you live and the conditions it could be clean as a whistle or dirty as Toby’s ass …

 

So turns out this hiccup only happens when AC is turned on. If turned off before starting it never happens. I’ll just turn AC off when I first start car for now on.