correct me if i am wrong,

i will be soon purchasing a grow tent that is 2x2x4ft, the cubic ft is 16f, for an exhaust should i go with a around a 60-70 cfm and for intake about 30-40 cfm. lights will be a 150w hps/mh for ventilation is this good enough?

I got 80 cfm by multiplying 16 square feet and circulating 5 times the room size per minute. I use passive intake, so I don't know about intake other than it should be less than outtake, which you already knew.

Man you want to vent 1/5 sq ft of your room per min. Compleatly bring in your sq ft Cubed every 5 min

by putting both fans as exhaust you will be better venting than if you had one intake and one exhaust so better just place exhaust fan and passive intake with a big hole

not 100% sure what passive intake is.

Forced intake would be a fan. Passive intake is using the main exhaust fan to create neg. pressure within the space by placing a opening down low in the space. I think in the tents they have flaps that open down low for vents. You will have to find a happy medium between the power of the fan and the size of the opening.
By the measurements given it looks like you'll need a min of 150 CFMs to exhange the air. I wouldn't recommend an inline booster fan or an axial fan as thier CFM's dramaticly reduce when any pressure is applied, either by adding duct work or too much neg pressure.
So I would recommend a 4in inline fan and a 4x12 Phresh filter or something equivelant. As long as the ambient temps aren't too high you should be good to go
Good luck,