1995 Chevy blazer 4 3 vortex high ref voltage and ground.
 

I recently did a tune up on my daughter's car. Replaced the alternator due to high output voltage. Now codes are popping up. First it was 43 knock sensor the 32 egr valve now 22 throttle position sensor. Now 34 map sensor. When testing all these except for knock sensor the reading I get for reference and ground are high. Ref is 5 volt but when I test is between 6.5 and 7. When testing ground it reads the same as battery at 16 to 17 volts. I am to the point I think the computer is going bad. I am not sure and don't want to just keep throwing money at it. Any help would be greatly appreciated.