hello i have a couple of issues i need to address for my Bonneville i'm sure you can help me

well its been a rough road getting my Bonneville back in shape, i spend alot of money and hard work on it but im still trying to pin point a couple of problems before it back to normal

changing out just about everything on the belt side water pump, idler, assembly alternator, etc shocks, most of the ignition system rims, (about to change again though) replaced the hood about to repaint the car again (paints not bad i just want black)

i need to find out where and what is shorting out my car when i plug a charger in my cig lighter it shorts out my radio and gauges and i stopped using the charger. so i need to fix that and how to fix that.

also my car is acting sluggish because i'm having a hard time keeping my engine from going past 20 and 40 after driving a long distance (e.g. 200+ miles in a day) i remember it did this before i switched out my top coil pack) so im' just figuring there all going out at same time. so i need to change that i believe

gas gauge is off by like almost a half quarter or more i need to know how to fix that because i burn A LOT of gas and i shouldn't be burning that much i just did fuel injection and changed filter but it seem like it only helped it SLIGHTLY
so i need to know how to fix that problem as well

um... also i need to know what els i need to increase performances?