High idle when shifting and when stoppef

[Upland54]

My 2000 Boxster 2.7 liter had no throttle response and throttle lag, installed new throttle body, throttle response fine, smooth stable idle, but now two months later it tends to go into high idle between gears and when I stop, about 1100 rpm when I stop, any idea what is causing this ???

[AZ986S]

CEL light on? Codes?

I swapped in a 74 mm TB and inadvertently cracked the AOS to TB plastic tube and had rough idle, high idle, and CEL light came on with misfire codes. All I can think is that you have a vacuum leak somewhere, loose boots. Check all boots and hose connection around TB and tighten hose clamps... But first check for codes.