as i once read on here . no turbo apart form a stock one is going to do anything on a 20det below 4000
my flat mate has a s13 with rb20det in it . r34 turbo good exhaust shit front mount good fuel pump . it made 190+ kw at the hubs on 11.5 psi . upon looking at the graph its not at full boost untill 4300. its not too bad when combined with the lighter weight of the s13 . car has run an 13.2 on shit tires and low hard adjusties