Back to the first page stuff I read about GA16de engines. Mine will rev to 7000rpm, however, the last few mph do seem to take forever. I'd say it's better to change earlier actually. However, changing as early as 5200 is stupid. Below 5000 revs it doesn't pull in any way. I think the 5000-6000rpm part is where the power is. Maybe early to mid 6000's is best to change. I've never really cared or took notice personally. Not enough power anywhere.