All my Glocks have the 3.5 Comp trigger pkg in them. In my G19 I also use a LSI Ti striker. Don't know really if it helps much. I usually go with Bar Sto or KKM barrels but of late I have been staying with the stock barrels. I would like to try and see what the max I could get from stock.
You can replace your 5.5lb connector with a 3.5lb connector. Part is about $10. and is very easy to do. I replaced my entire trigger assemblies with a competition trigger assembly from Glockmeister.com ($62.) . Also very easy to do yourself by just removing 3 pins and dropping it in. Takes less than 10min. Many also improve triggers by polishing connector and trigger bar. This however does not shorten length of pull. There are complete aftermarket trigger assemblies made to do this. Lightning Strike Products Inc makes one. The striker is used instead of a firing pin in the Glock. You can buy an aftermarket titanium striker which is supposed to reduce lock time and increase accuracy. Do a search on triggers at glocktalk.com and you will find much info. Hope this helps.