det suppression/ tuning tips

[slostar]

hey, heres what ive got: 1500cc 16v 4cyl engine with gt25 turbo. has a simple single stage wi setup.
at the moment its running just under 16psi with around 9 degrees advance on top a 10 degree base at that point. but has pretty much come to the limits of the fuel(95ron). as rasing the boost or timing gives light detonation. (listening through a detset) have yet to try retarting the timing some more and up the boost
was running about 180cc/m of straight distilled water. have uped the water to around 300cc/m but had little if any effect on the det. has 1800cc of injectors hitting a max of 75% at this stage. afr sits between 11.8:1 to 12:1 under full boost
is there anything im missing? or time to buy some race gas any ideas would be great.

injection point is just past the bend by the battery.