I've just started using Pre-MIX in my 13B-MSP. Smoother feel almost immediate after the 1st fill-up. I'm putting in bout 200ml (believe it's a US quart) for every 50 litre tank.
Like lennon said RM 60 for a 1 litre bottle to last 5 fill-ups.
the Quarter Mile Garage's R32 and Duke Garage's Z32 (both in 9 second club, japan) will be arriving tomorrow to take part in the sepang drag battle on saturday.