Sorry to jump on this thread, but I posted a very similar story in the tech Q&A area of the site, and as yet nobody had replied there!

After looking round came upon this post, as I am having issues with our ST170 very much like the OP

Car has juddering/hesitation when accelerating hard in any gear, not sure exactly where, but think it is between 3K - 5K but would need to check again to be sure

I was thinking of changing coil pack/leads/sparks but don't want to throw money around if it not going to help, and after reading more about it seem to think it may be the fuel pump/fuel pump driver module

Do you have to have the module coded to the car, or is it just a straight swap like the pump is?

Anybody have any ideas what else it could be if not the pump/module?

Just to add it has no error codes, and engine light is not lit

Cheers