My 408 now has FItech. My FE390 has 2 Holley 450 VS carbs. A thermoquad will not fit the 2x4 intake I have on the engine now, and for what FE parts cost I'm not swapping it anytime soon LOL. I'm going to focus on getting operating temps down to help lower the peak heat soak temps after shutdown. I may add a return-line style fuel filter to help clear the vapor from the fuel lines when hot. If I'm at or above 40mph, it doesn't seem to be an issue. But in-town traffic and lots of stop and go on hot days (we just got through a few days of 100-105F temps) seems to become a challenge. I only noticed yesterday that my fuel filter was empty at idle and it started to give me a bog when accelerating too, so it's something I need to dig into. I didn't build this engine, and I've only got about 1500 miles on it myself so I'm finding all the quirks.
2200ft in ID, 2k ft when I was in Vegas (I swapped to the FItech on my 318 while I was in Vegas). Might have something to do with it. I grew up at 4500' ft elevation so 2k doesn't seem high to me, is it? I hadn't considered elevation really, and it may be a bigger contributor than I'd considered. The second property is at sea-level, but that place deals with salt air and constant humidity (western WA state), plus lots of government mandated dumbness when it comes to ECO stuff, so who knows what they put (or don't) in the gas over there. Lately, I've been bringing my own fuel with me from ID, and issues do seem lessened to some extent (I've typically had to tear the small-engine carbs apart to get them working again - now I just have to deal with letting them soak in new fuel).
Never had any issues with my old kawasaki (the only trouble-free carb'd engine I've ever had), but my KTM seems indifferent to any additives and the carbs give me fits every spring, or after about a month of storage (I have too many vehicles, and I rotate depending on weather, so some might sit for a month in the summer). The KTM guys swear by seafoam, but that stuff has caused my more grief than it's ever helped. Just my experience.
I think the bigger difference is that it swings wildly here, constantly. Even in the winter, it'll go from the teens to the high 70% range and back again within days/week, and several times throughout the spring thaw. Then again during thunderstorm season. This year was the absolute worst I've experienced when it came to swinging back and forth, and it was obvious when I had to go through and get everything running again. Every metal item in my barn sweated and rusted horribly, which I've never had to consider in the past. I've not lived much in places that get above 30% unless it's actively storming, so it's been quite the learning curve. Maybe I'm blaming the wrong thing, but it seems like a reasonable variable to me.
