There are diminishing gains from a compression increase & you would no longer be able to run pump gas if you went that high.
You'll see much more improvement from increasing the displacement. The TR 280 kit or the Athena kit would yield a much bigger increase for the same amount of effort & not require you to buy race gas.
At the most, you might see 8% with race gas. With a big bore, tuning & pump gas you could easily see upwards of 20%