If you go back to my first post , you will see we are trying to establish if the problem is before or after your FI pump. That is the purpose of the test and sequence.
The damper and pre FI pump fuel flow system can easily be checked by doing the recommended 20 sec electric pump run test and post the results ..
If that has no effect , we move to the second test..you can jumper to the CSV as recommnended and post those results .. that will tell if we have leaking ball valves or vapor lock problem after the pump.
Your assumption that the later models did not use the modification 1 sec delay kit is not correct .. that is exactly the ones that the kit was made for .. they did not leave the factory with the kit b/c the kit was after all 113 production end and was a factory remedy for hot start vapor problems after short stops. The 230 came from the factory with a 1 sec relay, but its purpose was not a vapor lock remedy . It was starting aid. The 250 never had a 1 sec relay, as they used a hight temp CVS time thermo switch with a seperate rack relay that was not temp dependent .. that was eliminated when the R18Y pump changed the cone check valves in the pump to ball valves, as it was determined that this feature was no longer needed .. but , that is when the start problems came and that is why the kit came out .
Many guys favor a cabin manual sw over the 1 sec delay kit, as there is better control. The problem was aso helped with the later style pump, but there was still vapor problems , regardless , and mostly due to fuel filter hard mount to engine.
Do those 2 test and see if there are any results... this will help in determining your problem.