If you want to receive 2k Data inside two start-stop-signs, you can't use one PBP-command, you have to write a programm !

like this:
Repeat
Read 1 character
Until this is the start-character

ende=0

repeat
Read 1 character
if "this is the end"? then
ende=1
else
store the character
endif
until ende=1

And don't forget to use the hardware-UART !