My Yaris started this fault in May. It starts fine and most times pulls away fine, then at a junction when I go to pull out there is no power and being an auto just creeps and then after about 20 seconds (a long time when you are creeping out into a junction) it picks up. It can go for weeks without happening then all of a sudden it does. It is really scary and I have annoyed a few drivers who wonder what the heck I am doing. It has been with a garage, who are trustworthy and good with diagnostics, for 5 weeks and they are at a loss. They have felt it a couple of times but when they get it back and plug it in it has cleared. It doesn't do it once the car has warmed up, just for the 1st mile or so after starting. But it can do it again even if I have only left it for an hour. The technician doesn't think it is the MAS because it wouldn't behave like that and would do it even when warmed up. It doesn't have a MAP so that is ruled out, and he doesn't think it is the fuel system or accelerator for same reasons as MAP. He can only think it is the main control unit which he doesn't want to replace because it's expensive and he's not 100% sure. Has anyone ever experienced this and been able to solve it? I am too scared to drive it until fixed or I'll have to scrap it.