Fuel Pressure Too High at Idle

Yes, I've searched and couldn't find a suitable thread, so here goes:

My fuel pressure is reading 72 psi at idle and I need to know how to get it down to the required 58 psi.

I've got a 430 HP LS3 crate engine with a truck intake in a 2000 Silverado. The fuel system is the factory return-style with a Walbro 255 (TU432HP-2) that pumps through the stock lines (3/8" feed, 5/16" return) to a Corvette-style filter/regulator (WIX 33737) at the engine then through an Earl's 1.5" liquid-filled pressure gauge and finally to the fuel rail.

Yesterday I replaced the filter/regulator and that didn't change the pressure reading. The engine seems to run smoothly above 1000 rpm, but at idle (700) it hunts a bit and will stall with the clutch in coming to a stop sometimes. I can keep it from stalling if I downshift until I'm almost at a stop, but it will still hunt. I can't tell what the pressure is at cruising speed since the gauge is not visible while driving, but my AEM wideband tells me everything appears to be fine. At idle, the WB displays maybe .95 - 1.05 and cruising it reads .98 - 1.02, but for all I know the pressure could still be too high. All the info I've been able to find online tells me that this fuel system setup should be good, but in my case it doesn't appear to be.

So does anyone have any ideas on how I can resolve this issue? Will this pressure cause any damage to anything, like injectors? I've read that having the pressure too high at idle can cause the idle symptoms that I'm having so I need to resolve this issue before I look anywhere else.