1998 V70 GLT cold weather vacuum leaks

[crismit125]

Hey all, with the recent cooling of temperatures i have noticed some odd things happening with my car.
My brake pedal seems to be softer/spongy and easier to press, it feels like there is extra power assistance. This happens occasionally but other times behaves normally. The fluid has been drained and bleed out of air twice and if constant pressure is applied to the brake it does NOT sink so i don't believe this is the cause. Revs also drop slightly ~70-80rpm enough to see a dip in the tach and feel a vibration when coming to a stop with my foot on the brake. Finally and weirdly enough my gas pedal also is much softer and easier to press when all this happens, usually there is some resistance

what i have done so far maintenance wise
-PCV overhaul
-tried a 2nd used idle air control valve (helped the first 2 days but the issues came back afterwards)
-replaced vacuum tree seal

The only thing i can think of is a leaking brake booster vacuum hose and/or check valve. But would this cause a softer or stiffer pedal?

any help is greatly appreciated, Thank You!