@Tuxedoman no problem ;)

@overlord5453 It worked! Thanks so much! :D

@Tuxedoman okay, try this
-Actviate1 in engine group 1 and Activate1 in engine group 2. This way, engine group 1 will be active by default and when you turn on activate 1, engine group 1 turns off and group 2 turns on.
For afterburner, use this
-Activate1 & Activate2 or -Activate1 & Activate2 ? 1 : 0. They both does the same thing. By doing this, the afterburner won't turn on unless Ag-1 is turned off and Ag-2 is turned on.

@overlord5453 Apologies, I'll try to better explain what my issue is.
I have two sets of engine groups, I'll call them Engine Groups 1 and 2.
Engine Group 1 has an afterburner installed, Engine Group 2 does not.
Engine Group 1 is the default engine group that starts active when the plane first loads into the map. There is a switch in the cockpit that is connected to an Activation Group, and when it is flipped, Engine Group 1 is deactivated and Engine Group 2 becomes active.

Engine Group 1's afterburner is activated via a different switch that is connected to another Activation Group. The problem is that because the afterburners are activated by a different switch that runs off a separate Activation Group, the afterburners stay functional despite Engine Group 1 being deactivated.

What I am trying to figure out is how to make it so that the afterburners on Engine Group 1 deactivate with Group 1 when the switch to activate Engine Group 2 is flipped, that way, the afterburner can't be activated when Engine Group 2 is active.

I will try what you posted to see if it works.

@PlaneFlightX i think you missed something.

@overlord5453 What @overlord5453 said makes sense

@Tuxedoman okay let's say you have two engines. One primary and one afterburner which you want to activate when flipping a switch. But you don't want it to activate when the primary engine is active. Let's assume that primary engine's input is Ag-1 and afterburner engine's input is Ag-2.
In the input section of the primary engine put Activate1 and in the input section of afterburner engine put
-Activate1 & Activate2 ? 1 : 0. This way the afterburning engine will only activate when Ag-1 is off and Ag-2 is on.
I am assuming this is what you want because I didn't really understand what exactly what you are trying to achieve.

@overlord5453 Yeah I got that setup already, just need to find out how to to make it so the afterburner cant be switched on when the 2nd group of thrusters is active

Set zeroOnDeactivate in input part of the engines xml menu and set it to true. Actually you don't have to add it, it's already there. You just have to set it to true.

@PlaneFlightX since im not a nerd at funky trees, i ended up just tagging you, sorry if it's getting annoying though.