Looks great

It’s not a modification Todd, it is a chamber valve, it is an option on a German built Schwing(http://www.schwing-stetter.nl/images/fbp_21_24_26_en_kl.pdf)

 This is what Schwing say- The chamber valve permits using the concrete remaining in the line at the end of the pumping operations. A good way of reducing the amounts of non-usable residual concrete and a profitable and environment- friendly option.

 They come in 6'' and 5" sizes, we also plumb ours with water (from the hp water pump) so you have the option of putting water in the line for priming the boom, and blowing water through the lines after blowing out the concrete.