hey all just a quick question

alright when im driving sometimes if im stoping quickly and put in in N the revs die and it has stalled couple times anyway the guy from MMS said it was my bov apparently i dont know alot about wrxs since i have just brought it about a month ago but that wasnt the big problem
yesterday i started my car and drove out of my drive way tried to give it some stick and the car would not move just like a huge amount of lag and reving so i looked at the motor and the pod piping was pretty lose tighten it up and started runing much better but iv still got a huge amount of lag
does anyone know what this could be do i need a tune? new fuel pump or afm . also the car is a gc8 98 my 99

help would be appreciated