“Pretty fucking bored. I hate guarding - but, hey, things can't be that bad. A buddy of mine won it big at the tables and he's sharing the wealth, if you know what I mean.”— Tyler
Find weakness in Tyler's gang guarding the church is a side quest in Fallout 2.
This quest can be activated if the Chosen One completes the quest Get permission from Metzger for gang war.
Go to the church where Tyler's gang is guarding the chemicals. Ask about what's going on: you will need a Speech rating of 70% or more in order to progress the quest (having less than 70% only lets you give Tyler a casual greeting without consequences). Keep talking to him and eventually he will reveal that they are throwing a party.
When you return to Lara, you will find that you cannot collect your reward from her. Instead, she will demand that you help her attack the gang.