Idle surge after TB replacement and more

[1991GSXAWD]

I got the 63mm N/A throttle body from a friend on a trade(2 months old rebuild from tb.com) I replaced the stock 1g TB with it and now the car has high idle (4K rpm) on start up for 4-5 sec. than drops to 1500 and starts surging, I changed TPS,ISC and Idle SW with same results, put the stock TB back on and it idles fine, I'm at a loss on this one

 

[freeride_ca]

I'm having the same problem. I'm still waiting on my new ISC to come in though. My idle goes between 750 and 1500. high idle is about 2K.

 

[1991GSXAWD]

Problem fixed! It was my FIAV causing high idle on start up followed by surge. I replaced the FIAV with a spare one I had on my other TB Not sure how you go about testing one of them

 

[Tsi_User]

Problem fixed! It was my FIAV causing high idle on start up followed by surge. I replaced the FIAV with a spare one I had on my other TB Not sure how you go about testing one of them

This sounds alot like the same problem I have, exactly where on the TB is the FIAV? i know where the ISC is located if that helps.