'92 190E SLUGGISH TRANS

The synthetic transmission fluid, and filter I had put in last year, promptly, and slowly, seeped out, through gaskets and fittings, and caused me to have to add 2 quarts of Dextron when it was found to be low, 60 miles from home. I recently had fluid and filter changed back to Dextron I drove maybe 100 miles on this mix. with no problems. Now, instead of slightly pressing the accelerator to engage passing gear, I have to stomp on it. and when at 70 mph, if I removed my foot from the accelerator, the car would seemed to just coast, there is now immediate engine braking Does this sound like transmission damage. or a bad adjustment, or loose vacuum line? The same shop did all the work Recent: Cat, to back exhaust replacement Differential fluid change, clean vent bolt Transmission fluid change and filter. Thanks for any assist..................RIck