Posting this thread up here in case anyone decides to do what I did and buy the Lowe 57501 ICV - this is supposedly a replacement for the Williams unit (Bosch part no. 0280140501, which is no longer available AFAIK, with old stock usually going for insane prices.. if you can find any). Battling the high idle issue I bought one off ebay - unfortunately after plugging it in it only made matters worse. My high idle would "normally" be ~1.5k RPM, with the Lowe ICV, it jumped to over 2k RPM. Not good...