Mark,

THe ST170 (SVT 170 over here) has notoriously crap mapping. When cold the idle speed can go berzerk and be as high as 2200rpm then it becomes really irratic. The bogging down when pulling away is also a nasty charcteristic. If you get it chipped/re-mapped whatever you want to call it then it cures these irritating traits. I'm about to get mine done so I'll let you know how it works out.