Just installed issopro ev2 piro and boost gauges, 

Questions what fuse or wire ignition should I tap into?

#2 what wire can I tap into for dimmer....thank you for the help.

don't splice into existing wires..... just a new headache for later.

 

 Use fuse block add a circuit.  

 

you can get dimmed voltage on fuse 5 and fuse 14 ( i think) is already called gauges.