These last few posts open another subject well worth discussing. I build a lot of stuff that has to tolerate road spray and once a lot of marine wiring and there is simply NO FRIGGING WAY any kind of open connector (i.e. not hermetically sealed) can be tolerated. I haven't built an aircraft harness for decades, but as I recall, NONE ever used a sealed connection arrangement. In both OTR and marine environments it is often the open end of a multi-strand wire that has tremendously effective capillary effect that draws moisture with attendant corrosive ions (chlorides especially) that result in corrosion and stress corrosion cracking that causes the wire to ultimately fail. Why does this not seem to be considered in aviation installations ahead of the firewall????
I built racecars for a wide variety or series from Pro to historic, Baja, Pikes peak, various rally cars, etc. and wiring and connectors are a very simple thing really, that a LOT of people get wrong. I did beta testing for AEM, went to Motecs "school" about 25 years ago, have worked with almost every single aftermarket programable ecu in existence and many that are no longer made, built wiring harnesses from components, rebuilt "professionally built" looms, and thrown away very expensive junk that looked like the right stuff but was completely unsat. I have not built or sold the number of systems Ross has, but I have a very high level of shop and field experience. The reason AEM used me as a beta tester is I used more of thier products capabilities and went so much further than the basemaps that I found problems very few ever would, and I often could solve those problems. I adapted thier systems to fit engines they never intended for them to fit, and I am fairly sure they had a lot of "Did he really" moments.
First is lets talk about the ECU and wiring connectors/housings. The D-Sub connectors are fine for the ECU, as unless there is no other option it should be mounted in a protected location. Forget water or salt spray and think impact, shock, and other violence that will not bother the wiring but can and will give your ECU terminal issues. Now, I *personally* do not like D-subs, but have used them and in general do not feel the need to replace them out of hand.
My personal favorite is the Deutsch DT or DTM connectors and I favor the gold or nickel pins, crimped not soldered. The Tyco/AMP canon plugs using the DT/DTM style pins work very well, and are available in a lighter all-plastic version that locks securely. Not cheap, but then the point is to only need to buy them once.
Denso/Bosch/Metripac etc. connectors as used by most manufacturers are also fine for the most part.
Weatherpac connectors suck and just simply should never be used if it can be avoided. Same goes for the generic Molex connectors. Molex does make some nicer connectors, but for the most part they will cause more issues than they solve over time.
If we need a truly sealed connection then a DT or DTM connector with adhesive lined heat shrink over the wire side is hard to beat. Fortunately, we do not often need such things.
A side note on EFI in general- I get that for a lot of people EFI is a PITA mystery box that they have only the most rudimentary understanding of, and no desire to learn. That is totally OK, but lets try and keep objections or potential problems to the realm of reality.