Few Issues I Need Help With.

[R32/Ta22]

hi guys. there is a few issues with my r32 gtst. rb20det

first is today I went to go for a drive and it took a while to start and didn't want to idle right. couldn't get it over 2500 rpm without coughing and spluttering and the light cat/exhaust looking warning light was flashing? so I did a u turn and drove home. then I went to start it again to put it in the garage to have a look at it and it was totally fine... weird.

second could maybe be a cause of the issue. when I bought the car it came with a z32 air flow meter which has been put after the turbo when I believe its meant to be before the turbo. there hasn't been a problem with it in that spot but I don't know if it is causing lag problems or the reason for it to be placed there. my guess is it makes for a louder dose but I don't know.

also my intercooler piping travels under the intercooler then in then out the other side. I was wondering if I get an intercooler with the intake and out take on the same side I wont need the extra piping that goes under and around into the intercooler. the car is very laggy it gets onto boost at 4500rpm.

im only just new to skylines/imports so any expert help would go down a treat.