Well I think I have answered my own questions
From reading a lot of threads here and things online, looks like the Slyfox and Hewitt kits work pretty much exactly the same. The difference is that Hewitt comes all nicely wrapped up in a custom plug, and the Slyfox saves you about $100 by requiring you to splice into the existing wiring.
Rutech eliminates the purple starter wire used by the Slyfox and Hewitt kits, and adopts the Hewitt custom plug approach with a timer on the starter. Upside is that it is truly a 30-second plug and play, downside is it only is effective if you start within 10-seconds of turning to on. Wait any longer and the override will not function and you're back in code-city.
My 4Runner just started with the vacuum noise, and has not thrown any codes yet (three starts with the vacuum noise - which only made noise for a second or two before revving the engine and having the noise stop - been parked since.) I am hoping I've limited any damage they might have been caused (are the codes immediate?) and will likely go with Slyfox or Hewitt for peace of mind.