The exhaust is single. I wanted to go with 2.25" duals, but there simply wasn't enough room to properly route the passenger side pipe. The difference was noticeable on the drive home. With the single 2.25", I could hear an audible hissing from the exhaust under load, like climbing over San Augustine Pass by my house or when accelerating onto the interstate highway. I had the exhaust lengthened at the same time to exit all the way at the rear corner of the body, rather than behind the tire, to stop the gases from getting in the rear side sliding window, as they were doing with the stock exhaust.
My driving style? I have driven for a living for most of my adult life. Fuel economy is premium to me, and that's probably how I managed 8.4 mpg on my last trip in the RV in the mountains.
The idea of the 12v coil was for simplicity. One less thing to potentially fail on the highway. It's not a hotter spark idea, rather a "I don't want to be caught changing the ballast resistor on the side of US 54 outside of Liberal, Kansas" kind of thing.
I can read the plugs, and they show a rich condition. Not bad enough to foul them out, but enough to remind me that I am jetted for sea level yet primarily operating at 4000-11000 feet. This is changing in May, however, as where we are moving is only around 1,000 feet.
Further research shows that the fuel pump I was going to use does not supply enough pressure. The EFI unit needs 58 psi to properly operate. I am now looking at a different Holley unit, capable of 80 psi. The EFI has a built in pressure regulator for 58 psi, and I just need to run a return line to the factory return line by the original fuel pump.
(BTW: All backpressure is bad. Its a misnomer. All that is required is proper scavenging of the gases. This is commonly misidentified as a backpressure requirement.)
