hello everyone..ive got a red top rb20 in good condition..no mods..it did have a boost controller and bov but ive taken that off now so its full stock, bar a pod...sometimes when i start the car up..its idles fine but then the idle goes up and down..sounds like its about to die or something..the boost gauge is -19, -20 psi on normal idle..but then it goes to around -16psi..on idle and then it sounds like its about to die..wat maybe wrong with it?..any help will be much appreciated..thanks