LtSlayer

Ok let me start with saying I'm not a complete novice when it comes to mechanic work in general but was a little stumped by this. My car has an s13 SR20DET swapped and it goes through it's ups and downs. I noticed one day the car was significantly down power above ~3k and was leaning out as opposed to running very from earlier that same day and proceeded to replace every coupler and check my previous work with the rocker arms. Everything checked out but when I went to turn on the car I let the fuel pump prime. This is when I noticed the vacuum leak:

The car makes a hissing sound coming from around injector 1/the fuel regulator as the motor primes. I'm no referencing the hum from the pump but an audible hiss from around there. I didn't see or smell gas and soapy water didn't spot it either.

I've read something relatively similar and it was the O-ring on the fuel injector but I swapped this injector 2-3 months ago and never replaced the O ring. Could this really be the problem?

Any other ideas?