Either it's running out of fuel when it needs it the most or it can't breath (either in or out) the volume of air air it needs at higher RPMs.
You need to investigate each possibility and VERIFY that it is good, not ***-U-ME it's good just because some part or another was changed, modified, or replaced.
Kindly put all relevant details like what has been done or tested (along with the results) out there up front. Extracting details piece-meal, like pulling teeth, isn't very pleasant. Also, feel free to use the "Edit" feature to add to prior posts. This isn't Twitter, there's no 140 character limit.