Does anyone know if it is absolutely necessary to have a relay on the power side for direct fire leading ignition system modification

 

It is not necessary, so long as you disconnect the battery when the engine isn't running. PIA for a DD, but maybe practical for a race car.

I disconnect my battery if I am through for the day because I don't drive the car everyday.

 

why would the coils suck power if the are connected to key on power?

 

That seems like something may be misconfigured.

They shouldn't. To answer your question about needing a relay or not.. It's not required but it's added to ensure that you get full battery power to the coils. Otherwise, you are powering them via the ignition circuit. Anecdotal but currently, I don't have a relay (I should add one) and I can start the car after it's winter break no problem. I don't disconnect the battery and winter break for me is about three months.

 

I wanted a simple solution to disconnecting my battery as I don't drive my car often, and store it for about four months in the winter. Bought a master disconnect switch off Amazon and it simplifies the process.