The fast idle waxstat tends to seize when old so the stuck mechanism keeps the throttle partially open in "fast idle" mode, even when engines warmed up. Ppl tend to just adjust the idle screw to without resolving the main cause.
Hence reason for removing the waxstat mechanism is to allow the throttle to fully close and let the IAV control the idle since it does the same job. And thus why you also need to clean the IAV and readjust the idle screw.
Reason for bypassing the TB coolant pipe is to keep the TB cool = marginally cooler air. The coolant originally ran the fast idle waxstat hence you have to remove the mech after bypassing. Plus the coolant kept the TB warm during extreme winter.
The teflon inlet spacer is more effective imho cos it prevents the hot engine from heating the entire inlet mani & TB hence much cooler inlet air
Oh and yes as skinner says remove as much unessential weight improves all performance free. Replace spare tyre with tyreweld, remove back &passenger seats, carpet, bulkhead soundproof, etc depends how much comfort ya wanna lose