Funny idle - one for the experts

Does anyone know what could be causing idle to rise some 200 rpm - i.e. from the usual 800 to some 1000 - when car is warm? If I leave the car idle it
rises itself, but if I push and release the accelerator just a notch, idle is back to normal, then if left to its own devices for some seconds, idle will suddenly and for no reason rise slightly once more.
I remember the throttle body was a real nuisance to align when I had the car chipped. Plugs were replaced to no avail. I'm still running the stock '98 BPV. MAF has never been replaced.
Mileage is normal, idle with a cold engine is fine and rock solid stable.
The only other thing is some slight surging at WOT in 5th. At throttle a little over 3/4, there is a very thin band where boost seems to be getting on and off all the time when engine is coasting a slope and surging is very obvious then but at WOT it is very much less noticeable.
Thanks in advance,
JP Roberts
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

from
car
very
I've no idea but someone might know ......if you tell them what car we are looking at!
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Good point! Since I'd been posting rather often I seem to have forgotten to mention I've got a '98 1/4 A4 1.8T Q.
By the way, a friend of mine's Vag-Com throws no codes on it, as we could see yesterday.
Thanks,
JP

it
idle
idle
'98
stable.
getting
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Well, thanks to all of you. I really didn't know the difference between OE and OEM, though if it's Brembo it must be better than OE, can't it?
Yours,
JP

from
car
very
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Sorry this one went to the wrong thread!

it
idle
idle
'98
stable.
getting
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.