I recently retrofitted my AC with R-12 and when the compressor kicks in I have a loss of power as well. You could check your AC belt tension. Buy a kirket for 10 bucks at napa. AV tension should be about 80 pounds. I have an 81 300TD and after timing chain, tensioner, rail, valve stems, valve adjust, injector cleaning this is one of the fastest vehciles I have ever driven. After actually looking at my injectors I can tell you injector cleaner additive will do little to nothing for dirty injectors. It may be is good maintenance, there is debate on this. I bet my car will do 120 and acceleration is awesome once turbo kicks in. Are you running oil, this also changes things? Don't be afraid of these jobs, take it one step at a time, you won't believe the difference. Ohh I have 240,000 on mine.