94 suburban electrical

At first my wife told me that the wipers didn't work all the time. then the abs lights would flicker as the wipers ran. last week i replaced the fuel pump. on Thursday she was going out of town and a friend of mine tested it said all the problems where due to a poor performing alternator. new alternator and she has all of the same problems. on Friday the speed ometer started moving all over would read 30 when she was sitting still.90 when she waqs doing 35. Saturday she told me that there was no power and it has flames out of the exuahst. When I drove it all was fine till the rpm's came up to 3500 then it started to sputter and pop. now the fuel pump will not come on again and the speedometer reads 90 when you turn the key on. i replaced the main computer and it has all of the same problems.:banghead: