Sudden Poor MPG

Hi folks,
I have a 2001 Dodge 2500 SCLB Auto 24v with 297k, It has a Suncoast converter with fresh rebuild about 10k miles ago. Had a reman VP pump 100k ago along with a FASS with 14 psi idle and 12 psi WOT. fresh filters last week.
Has 3.55 with 285 Terra Grapplers. Edge Hot Comp, 5 inch turbo back straight pipe. basically stock other than that.

I bought truck off good friend early october. He had truck for 6 years of which i have know him. I actually helped on alot of the work.

I used to get 15 to 16 in my mostly congested rural area. It started to drop a little. Now for the last 2 week it went straight to 10 to 11. I have to baby the crap out of it to squeak 12 outta it. I have the scan gauge on it with it tuned in correct. and the gps verifies it with hand calc.

I hear what i think is a boost leak somewhere. i felt all boots cant find anything obvious. im going to make a tester tomorrow. Now the sound seems to come and go, but is more there then not. and when its not it seems to get better instant mpg. i did the apps reset. nada. i did the 2k ohm iat, and might see a mpg.but only in the morning. once its warm there is no better mpg. my buddies with diesels didnt see a drop from fuel.

So could a boost leak make a 4 to 5 mpg drop in mileage. my buddy drove 60 mile trip to work everyday and would see 18 -19 constantly. just started dropping in the last few weeks bad. noise is best described as a whosh sound under the cowl. Increases with rpms. sometimes there at little boost, sometimes is louder.

could my injector be worn? its always had loud clacking but its been that way for 6 years? im thinking of doing 100 hp nozzles? but wanna get this figured out first.

Thank you.