From my memory (I know its getting worse ) I did not remember Seb's car going over 21 PSI at JWT..... I do not have the graph here (Seb has it at home) Seb said he remembered 21 PSI also. So I apologize if that info is wrong. I thought I remembered it only holding 19 PSI to red line? I know the high load timing was 18 degree's. I think in Seb's case he is restricted by the inlets and outlets on the stillen intercoolers and just making the ends a true 2" pipe would help him. I am sure by your data on Dee's car he would benefit from your intercoolers and piping even more.
Do you think it is possible you went too large on the pipe at 2.5"? I am wondering if 2.25" pipe might offer the greatest gains at this power level? BTW: Awesome Job on Dee's car!