I've never really been able to see a vacuum leak with a gauge.
I doubt you have a leak though. YOu put on a go faster mod and are likely enjoying it. Therefore the uh...6-7 gallons you are burning every 2-3 days doesn't seem like all that much. Back off the throttle and you'll see it improve.
As for the tune. Keep in mind that yoru Gen 3 M90 pushed 90 cuibic inches of air per revolution into your motor and your Gen V M90 is also pushing 90 cubic inches of air into your motor.
The only difference is the Gen V is sending a cooler more dense charge in. There shouldn't be a large fueling difference. the biggest difference is usually in the driving style.