My 2004 Honda Element, 500kplus miles,  automatic, displays 2646 code. The motor and transmission have been replaced in the last year or so.. I have had the VVT valve replaced repeatedly since this issue began.  Dealership parts last a few weeks and cheaper ones even less.   Noone seems to be able to figure out why it keeps happening.   I drive lots of cross-country trips, hence the high miles, but bought it new and have always take great care of it.  No racing around, all regular maintenance has been kept up with.   Problem: I get on the freeway, step on the gas to pick up speed, anything over 2800 rpms and it seems to lose all harmony in the drive train.   Like the cylinders are confused and fire out of order.  The vehicle sputters and bucks...When I let off the gas pedal the rpms drop and I can very slowly gain speed but once up to speed no passing if more than 2800 rpms are required.  

I searched but see nothing on this issue in the posts. Thank you to anyone who can help.