OK, I see one problem with your formula off the bat.
If(AirfilterToggle.Value=true && BatteryToggle.Value=true (“true”),(“false”)}), “”)
There is a right curly bracket that probably shouldn't be there since there is no left curly bracket shown. Also there appears to be a missing comma between the If() function condition (Airfilter.Toggle.Value=true) and the result of the condition when the condition is true. The syntax for the If() function is: If( Condition1, ThenResult1 [, Condition2, ThenResult2, ... [ , DefaultResult ] ] )
If(AirfilterToggle.Value=true && BatteryToggle.Value=true, “true” , “false”)
I believe my restatement of your formula says that if both toggle values are true, then the return value "true" will be put somewhere and if either of the toggles is not true, then return value "false" will be put in the same location. Since the two options are mutually exclusive, therre would be no need for a default result so "") is eliminated. Maybe I'm missing something but If this is not correct, let me know.
My browser doesn't let me follow the If() statement beyond what is shown in the box. Could you please isolate the offending statement with the error and repost it.
BTW, my process for debugging formulas is to isolate each phrase and test if it works, then start connecting them.