I also have Walbro 255, SOS regulator, ID1050x. I'm running 16psi on a slightly lower comp motor with SOS stage 2 kit. Injectors are at 90% duty at redline. Right around 500whp on Evans dyno.

 

The AEM 320 pump is a good choice as well in my experience and its quiet. I have run them NA and supercharged as just a standard OEM alternative. The 255 may pull a little less duty on the factory fuel pump wiring though for what that's worth. I've run with and without the SOS pump wiring in past, and honestly if I had to do it again, would opt for whatever option pump I wouldn't have to do that. I went through a lot of shit to get that SOS "upgraded" wiring to work reliably and ultimately ended up bypassing the re pinning of the pnp plug entirely and running direct. The car left me stranded a handful of times until I could get to the bottom of it.

As far as the pressure/power. Depends on what blower you are going with as I didn't see it specified? 1220 or the 1200? At either event, in general I've found the pressure to pulley size on SOS website to be inaccurate by at least 1psi at Sea level. In other words if they say you will make 10psi with the 4" pulley, expect to see 11. That said, either blower will offer you the power you want, but the 1220 peak efficiency is in the 6-9psi range, and the 1200 is happiest at 10psi + and this all equates to more power at less pressure with lower IAT, so I would just say do the $75 upgrade to the larger 1200 blower, it will run great at 10psi and offer a lot more headroom and arguably better resale in future if you ever decide to part with the kit. 10psi with the 1200 should get you 375-390whp on a typical gas tune on a average reading Dynojet which is what most figures are based from for reference.

 

Yeah from everything I've seen with the SOS wiring kit, I wasn't happy with it. I understand the philosophy behind it from SOS's standpoint in terms of making it somewhat user-friendly and easier to understand and install. But the reality is it isn't the best idea to leave MOST people in charge of doing their own crimping / wiring; especially when it comes to critical components like fuel pump wiring. That said, even if you are adept at wiring, ultimately the supplied relay is physically too small (smaller pins & sockets), and realistically the current draw becomes too high for the OEM top connector / smaller relay to handle after enough amperage, which I'm assuming is cars running the larger 450 - 525 Walbro pumps beyond 550+ whp on Ethanol.

I built my own PnP kit using high quality components, and a physically much larger Hella relay. Regardless of all of that, the limiting factor is indeed the top connector for the fuel pump. If I could go back and do it all over I'd most likely drill a hole through the pump carrier and run one of those bulkhead fittings specifically made for running fuel pump wires. At this point my pump is installed and I don't feel like crawling through the trunk. If it fails though, that will be how I'll go about it next time.

 

Thanks Kyle and s2kJunky for sharing your experiences. I was going to run the Walbro 450 (been waiting as it's on backorder) due to future proofing and possibly running e85 down the road, but maybe the better plan is to just run the Walbro 255 and cross the bridge of rewiring and a bigger pump if/when that time comes. It seems like some folks have had issues with the rewiring kit and one less thing to worry about is a big plus, especially since I'm not looking to make big power.

 

1000CC with 255 will carry you to 500whp, add a inline pump or BAP with a return fuel line for 600-700