Possible electrical issues

Since I've had the car it sputters. Lately the car has been shutting off on me while driving or even stopping at a red light. Sometimes I have to throw it into neutral before I come up to the light so I know that the car will not shut off. Also the check engine light has never been off for more than a day since I've had the car now, which is going on for months. The check engine light is random misfire. I have changed the spark plugs, I have changed the wire to it as well the plugs. I have also put in a new camshaft crankshaft sensor, ignition coil, also alternator, radiator, thermostat, water pump, all new three belts. Oh, and my gauges and my speedometer work when they want to. Sometimes I hit a bump and my speedometer work and then there's times that the same bump will cause the gauges to no longer work. So my gas will go empty and my car's temperature will go cold even though both of those things are not true. Sometimes I'm driving the speedometer will go to the speed that I'm going and then it will be like ping pong it goes back and forth. 0 to 70 then 70 to 100 and this is all while I'm driving. Lastly the reason why I think it's electrical is a lot of the time when these problems start happening I will start messing around with the wires inside of the engine and the closest location I can tell you that I will mess with them is over the camshaft sensor on the 1997 sohc engine please any advice will help I don't have much money that's why I've been trying to do this myself I had a friend helping me but he fell off since I've changed the battery connections because I used to have a 4 gauge wire going from the fuse box to the battery. It is now six gauge and the connection has been improved but the car will sputter on occasion as well as losing power on occasion. This is the last month that I have to get it registered, but I can't get it registered until that check engine light comes off. Please any help will help I would pay the $20.00, but I barely have that for the repair manual you guys offer. Thank you for your time.