Electrical Issues.

[DSM-is-LOVE]

My Spyder is acting up in such a terrible fashion. So about 2 months ago I got a tune done by Shane at DB. He said before he could get the car back to me it needed a new battery cause the old one was shot. So I took the old "Yellow Top" Optima out and shane put in the new one and then gave the car back all tuned and ready to go. I never usually let my car sit for more than a day or 2 without driving it. Well, I let it sit for 3 days in my parent's garage, and the battery was completely dead. I put in on a tender, and watched the needle bounce for half an hour, which means the cell is dead. The new battery I put in was a "Red Top" Optima. When the car was running and driving, Sometimes when I would cruise down the road, the dash light, and headlights would flicker, but only at certain RPM's, as well as the higher the RPM, 2 of my dash lights would progressively light up. As well since the battery has died, my check engine light came back on, but my tune was still there.

I don't know where to start looking. I think it is a bad body ground, but it seems way too worse... Any idea's or help with where I could look, or start to look?