Hummingbird Free Plugin slowed site down

Good morning, Previously downloaded FREE Hummingbird plugin and found it great for identifying particularly images that were potentially slowing down site. Fixed those image sizes with combination of Smush FREE and reloading the larger images to the site and re-applying.
Did Gzip compression and saved settings. Site immediately bogged down. Did Pingdom speed test and found results previous to now dramatic ie 8.1 sec load prev to 41 sec after Gzip compression from New York server?
Are we able to undo these changes? I see that some people have found a similar issue when the same tool is used on their sites?
I look forward to your prompt response when convenient.
Kind regards, Peter