I'm having trouble with m s1 rb25 also..drives fine, idles fine new oil, plugs etc etc
Specs as follow.
Hks super dragger
Apexi pfc
Pod filter (3A racing pod)
Split fires
Decat (standard cat modified)
Fmic
Running 0.7 bar
Bcpr7es gapped to 0.8
Runs fine until I go to give it some feels really sluggish and sometimes feels like it shudders
Been like this for a while I can't find the source.
Any help would be appreciated.