P1235 help please

[SOCON]

In the 7 years I have owned my car this is the first time it has totally stumped me and I have no further ideas where to look. So about a month ago started getting P0172 and P1170 codes. Bought an injector cleaner and ran the port injectors with no change. So pulled the supercharger and sent GDI off to be refurbished. 2 were not serviceable so bought a brand new set of Hitachi injectors. While apart I replaced the Edelbrock T-Map harness which had been damaged by a shredded serp belt some time ago. Replaced My old Delicious blue coils with a new set of the same. Found a badly cracked weld on mid-pipe and had that rewelded. The cat appeared badly burnt and broken up so it was gutted. Put it all back together and now it will run 8 seconds and toss P1235 and go into limp mode not exceeding 1500 rpm. So what have I tried?
1. Data logs show fuel rail pressure 19.8 bar for 8 seconds dropping to 2.5 to 1.8 bar and then rpm hunting after about 30 seconds.
2. Bled fuel rails best I could
3. Checked many times very thoroughly for leaks
4. Disconnect battery and idle relearn
5. More data logs. All sensors seem to be responding correctly. AFR vs Target seem ok until HP fuel pump drops out then off scale lean as one would expect.
6. Ohm HP pump coil. In spec
7. Ohm harness from HP pump to EDU. In spec.
Hypotheses, Something is cutting power to HP pump at 8 seconds after start and I have no Idea why. Any help will be greatly appreciated.

[DarkPira7e]

If you're logging, check to see if the fueling mode (0, 1, or 2) correlates with the fuel pressure dip as well.

[SOCON]

Fueling mode switch remains 0 for full 60 second idle.
Injection mode from start ~2.5 seconds is 3 and drops to 2 at 8.096 and to 1 at 8.66 where it remains to the end. Major pressure drop at 7.71 seconds so right at 5 seconds of engine run time