Holeshot makes a slip on??? I didn't know that...
If it's set up like I'm imagining it is then eliminating the crossover will reduce HP by eliminating the scavenging effect of the crossover......The cylinder that last fired, it's exhaust pulse helps suck the gases out of the next cylinder, on so on.....
Search "Cobra Slip ons" Hands down HP killer.....It's a slip on that turns the factory exhaust into 4 individual pipes and mufflers and is known to reduce HP probably 10hp at least....
Don't worry about "targeting" where your a/f is coming from, they don't even do that on huge HP F/I cars, usually only one bank of a V6 or V8 is being read....I've seen it done on all cylinders but only by guys who are "Guage Junkies"" with lot's of money to burn.....
You gotta take it on faith that whatever tuning you have done is consistent from carb to carb and cylinder to cylinder....after that plug condition should tell you if you have a particluar cylinder that's not playing well with others......
If you want to get individual cylinder readings for some sort of troubleshooting purposes maybe??? You could weld bungs in in front of the crossover on the ind. pipes and move the sensor around as needed, but gotta make sure it's not too close to the exhaust port, your installation manual should give you a numbers for that.........
I've not seen the holeshot slip ons, are they similiar to Kerkers in that the factory garbage/collector can is done away with, then 2 pipes into one going to two mufflers, ????, But with the addition of a crossover after the 2-1 junctions, which Kerker does not have??????
When I ran an a/f guage on my stock exhaust I installed it directly into the factory collector can, that big box that looks like a 1950"s Kirby Vaccum Cleaner.
I now have it installed in the mid pipe on one side so that it reads the front left cyclinder and the rear right cylinder.