VS slow to return to normal idle after starting

Cheers i've got one more hose to check then back to the iac i think could well be faulty or the wrong one as u suggested the lad at my local repco isnt too bright and has given me the wrong part b4

 

So after a couple of weeks checking for vacuum leaks etc, changing the IAC again, i'm still no closer to a solution. I still get high idle on startup and is slow to drop to normal idle. It was suggested to me to check the base idle and after following procedures on here mine idles around 1400 at the point it should be 450-550. There are no vacuum leaks to be found in hoses after extensive checking of hoses and also taking of hoses 1 at a time and blocking the inlet. Is it possible for a air leak inside the throttle body either around the butterfly or IAC?

 

yeah throttle body is spotless u could eat of it butterfly moves freely idle screw eased off as far as it will go only reason im thinking air is getting past inside throttle body is after following the base idle reset procedure its idling at 1400 when it should be close to stalling and am not sure if im hearing things that aren't there but when putting my ear close to the throttle body/plenum it sounds like air getting sucked through

it drives and idles fine just high revs on startup and when changing to drive

 

im keen to sort this out because a)its driving me nuts and b) it doesnt seem to be very common but after several searches there have been other ppl on here posting the same problem but nobody has ever followed up with a fix

 

Thanks, have already wasted a can of carby cleaner looking for leaks have recently had intake manifold gaskets changed and was doing the same thing before and after

 

When setting the IAC length to 25mm what point do u measure from the base where it joins to the TB or fro the endof the plastic bit which goes partiallu inside the TB

Cheers