My 2005 Lexus GS 430 has developed a fault after a recent 100,000 mile service at my local dealer. The auto ‘box oil was changed as part of the standard service, and whilst normal driving is fine, I've noticed that acceleration is noticeably sluggish. I'm 100 per cent certain this did not occur prior to the service, so assuming it’s something they’ve done - Any ideas what it could be?