i have a 2004 impreza wrx. i have a factory turbo guage. when 4000 rpm hit my car pulls hard then once the rpms get above 5500 the boost drops fom a little under 1 bar to 3/4 bar. then once i get over 6000 it drops to 1/2 bar. is this suppose to do this or is this normal. should i take it to the dealer. i got it from green valley auto, i heard some bad things about them where should i take it? please help...