Holley sniper
I’ve decided to eliminate the 2 prong ballast tie them together and tie into that for my power to the sniper.
I know I answered here already but when the new reply alert came up I re-read your initial post and missed the part about the main power and ground - do not do this. Will it work? Mostly. Will you have problems because of it? Yes. Perhaps you missed it in the instructions - it only says to connect the Sniper main power and ground directly to the battery like 732 times.
It seems like you're making this harder than it has to be. Make the connections as described in the instructions. Again - forget about a diode in the start circuit and just tie them together like they want it. You will be much better off in the end if you follow their instructions. 99% of all their 'failures' and subsequent returns are due to "operator error" and not the parts themselves. Don't be that guy!
If you ever have to call Holley tech support, the first question they will ask you is if the Sniper main power and ground are connected directly to the battery. Should you follow through with your plan to use the start circuit for you main power, your answer would be 'no.' Their answer would then be, "sorry, we can't/won't help you until you connect the main power and ground directly to the battery."
The main reason they want the ECU power and ground connected directly to the battery is because the Sniper is susceptible to RFI. RFI can and will wreak havoc on it. The main ECU 12V source has to be 'clean', meaning there is nothing else pulling power from your connection point - the battery is basically the only point in your electrical system where that is 100% true. Some will argue this but anywhere else (including the starting system) is not going to be 'clean', at least for the purposes of getting the Sniper running properly. Any suspect wiring or connections will only increase the chances of RFI happening. It's not always obvious either until you start getting into data logs trying to figure out an issue.
I helped a neighbor install a Sniper on his Brand X machine. His wiring was a mess, the battery cable was attached to the lug by one single strand of copper. Before he even started, I urged him to re-wire the car or at least the parts that were related to the Sniper. He did not want to hear that. His ego got in the way because he'd been around the block and knew better. Against my advice, he installed the thing on his own and guess what? The car would not start. After several attempts to figure it out including hours on the phone with Holley, he was ready to throw the Sniper through the window. Eventually he relented and re-did the wiring like Holley said and wouldn't you know it? It fired right up. 100% true story, no exaggerations.
Don't mean to come across like an ***, just trying to save you or anyone else reading this endless headaches. Good luck.
