That trigger spring (brown with a spring in it) is the culprit. Otherwise known as the NY1 trigger- so NYC cops could not shoot the Glock without thinking they had revolvers. Silly device--decreases risk of shooter hitting anything or shooting anyone.
Take the brown thing out and try it again. See how you like it after, and report back.
You do not achieve a 3.5# trigger by just a connector change alone-- that's why Glock changed the name to (-)-- you have to do other things that are not worth the compromise. You will have about a 5# trigger.