My Lil bro just bought some diprocol gauges and I need to know what size of drill bits and tap I will need for the install for the pyro and the boost. No we do not have a boost bolt, we were just going to install it on the elbow.

 

Most of them are 1/8" NPT. You're supposed to use a letter "R" bit, but 5/16" will get the job done.

 

A 21/64 drill bit is the one the NPT tap says to use. But I imagine what wannadiesel said will work too.

 

Is most boost and pyro use the same taps?

 

Most are 1/8" but some pyros are 1/4"
No need to tap for the boost gauge, there are plugged ports you can use but we need to know what year truck you are dealing with to point them out.