General update on progress of this install.
We have made three attempts to get this correctly working. The pressure this pump can generate is very impressive and this has actually made it harder to install (more so than its slightly larger size, we think).
Our first attempt was to basically replicate how one would install a 255 into the STi GR in tank fuel plastic basket housing. This quickly resulted in the pump shunting off to the side and pulling off the fuel line. Our second attempt included an extensive 'remodeling' of the internals of the fuel basket - cutting out most of the filter housing on the side of the tank (no longer needed as I have an in line Aeromotive filter). This let the 416 hang more naturally in the basket. The photos below show this (with out the external housing of the basket, we do reattach this before reinserting into the fuel tank so it is not like a Full Blown Hanger with its slosh/surge issues). We also switched to a fitting for the direct power lines (this can be seen in the photos with the large gauge wires still not connected to the fuel pump). This seemed to work well for a time but eventuallly the impressive pressures this pump can generate pushed it off the fuel line again. Our third attempt involved fabbing an in-basket hanger system that more rigidly fixed the pump in place. We also used a longer section of fuel line (from the underside of the basket lid to the pump) that placed the pump firmly against the bottom of the basket.
We tested this setup for several hours by crimping off the fuel line just before my Aeromotive regulator such that a constant 100psi was created. We let the pump chug away at this pressure. We would also occasionally tweak the fuel line crimpers such that pressure surges were created. These pegged the gauge on my regulator and so were likely well above 150 psi. Amazingly, the pump never went into a fail safe mode while we did this. After doing this we rechecked the install and the pump had not moved nor had it slid off the fuel line.
I have been driving the car like this for a few days, including a spirited canyon drive, and everything seems solid. A/F correction is good, base fuel pressure is the 60 psi my injectors and tune want, etc.
However, we do still have the stumble/stutter at very light throttle as discussed in my next post...
Photos of the 'second setup' (sorry, we dont have any of the final install where we fabbed an in-basket hanger system and lengthened the fuel line so the pump is pushed against the bottom of the basket)