Acceleration and fuel issues?

A few weeks ago, I had an oil change and A/C check from a garage. They spewed A/C refrigerant everywhere from a broken line somewhere. Not a big deal, I had to take an important trip so went on and drove 500+ miles over 2 days no problem. On the third day I get home and it starts to lose power when accelerating at speed. A couple days later I'm flooring it to get it up to 20 MPH. My mechanic said it was the spark plugs, so changed all 6. Then he says it's coil packs so change the 2 he said we're bad and 2 more that looked iffy. Now he says injectors are clogged and to put cleaner in the gas let it sit for an hour run it for 20 minutes and repeat daily for the next 3 months and may clean it out. I don't know if I believe that. It's developed a hesitation when starting, occasionally shuts off at intersections unless I'm giving it gas, and almost behaving like a manual transmission. I floor it to get up to 20 over a half mile then let off the gas and it shifts usually and can do that again until I top out at 45mph. At idle in neutral revving the engine the tachometer surges between 3.5 and 4. Is it really the fuel injectors or is it likely something else?