drag manifolds suck...the greddy kit the way it comes sucks, I would go with rev hard. tuning is fuel system, boost, timing, etc. you will lose gas mileage for sure but it is worth it. here is what I would look into buying if I were you:

REV Hard stage 2 kit
hondata
3 bar map sensor
720cc to 1000cc injectors depending on where the future goals are
255lph fuel pump
and of course gauges, timer, boost controller

with a LS block as long is it is in good shape can run 14psi on pump gas if and make 300whp or so just make sure you run good gas and make sure the motor is solid before you start