I'm looking to get a 5/16 spacer, z tube and pop charger and was curious if anyone had or has this set up and can clue me in to their actual gains to see if this set up is worth the effort. Any opinions or experience with this would also be greatly appreciated.

The spacer on a non rev-up will give you up to 20hp from what I hear. Ztube and intakes are good for possibly only a couple hp at most but it does sound better.

if you have a '06+ rev-up then you will want to look at the MREV2 manifold to go with the spacer.

I have the 5/16 spacer and z-tube with k&n high flow cone on my '04, and the spacer made a huge difference- I'd say 15-20 whp gain is legit. It gives an easily noticabe bump in power across the whole tach. Overall a quick worthwhile investment for an older non rev-up 'G35

Shop G35 has R2C intake, 5/16 spacer and HKS axle back with UpRev Tune. Without the tune you are going to run dangerously lean.... we tried the Hypertech unit and it did its best to correct a/f, but you have no way of tuning any further. Went the Uprev Tuner route and from the dyno you can see the difference between the 3 options.

G35 Uprev Dyno Comparison

^^^ What he said

Thought about a spacer but my son said go with Kinetix Upper Plenum instead. Glad I listened to him for a change! about $50 more than spacing but a lot more air to the front side means more power and less heat.