You want the poly..

As for upgrades maf upgrading is good bit this also depends on what future plans you have with the car.

First things first get the transmission side of things right.

If you're gonna do anything get a LS1/2/6 intake manifold swap so you can benefit from a better maf. I would also recommend you get a downpipe at the minimum. 3" not 2.5. And you will need tuning...which is the most important part