TBI conversion on a Ford 400 - need help getting it to run

[Dr_Grip]

Hi guys,
complete and total newbie here. I am trying to get a homebrew GM TBI setup running on my Ford 400 and it seems like I hit a wall by now. I really appreciate some help from you guys.

So, what has been done so far?
-I got a TBI system from a 1990 5.7 K-Series truck (7747 ECM).
-Mounted it on the engine's Edelbrock Performer intake
-A Ford DuraSpark II dizzy is connected to a brand-new HEI module (getting a perfect spark at the right time since putting the wires the right way 'round :D )
-Fuel pump's an Airtex E8094
-New coolant temp sensor, IAC, O2 and MAP sensor are fitted
-I did not fit a VSS
-Tested the TPS, it's good.
-I used TunerPro to set the BPW to 161.5 to match the displacement and disabled the EGR (based on the ARHT bin)


Sooo, what happens so far is that the engine starts up nice after a bit of cranking, idle's a bit high at 800-ish (but as I did not set base idle yet and the park/neutral switch isn't connected, that's not too much of a problem, I think).

When I try to build up revs slowly, the engine will hold any given speed (1500, 2000, 2500rpm, etc) only for a few seconds before losing revs (massively leaning out?). Furthermore, suddenly stepping on the throttle leads to violent backfires through the intake. The ECU is not throwing any codes. Any ideas what might cause this?

Once running, fuel pressure sits at .9 bar/13 psi, just as it should - but it takes about 10 seconds of cranking to build up fuel pressure at startup. Is that normal or does it indicate a problem with the fuel pressure regulator (most likely unrelated to issue above, but who knows)?

As I said, I am a total newbie when it comes to EFI, so I am at a loss here. Any help is very much appreciated.