porting and polishing

[endoxr4x4]

how much difference can be expected from porting and polishing heads and intake on my 4be?

[Boosted LS1]

To what spec? Polishing is neither here or there so that's just about bling. As for the porting, what's being done? Are you getting revised valve seats and or bigger valves? If you'r not sure then who can say what gains you will get? I can stick a flap wheel down the ports and whizz it about but the gains wouldn't be great.

You need to ask for a bit more information from the porter guy.