More Timing need more fuel?
 

When you advance timing thats going to require/ and consume more fuel. Correct?

Not always.

More timing to burn the fuel you have in the chamber already...

Not necessarily. Fuel/air is a fixed quantity. Timing is adjusted around F/A, not the other way around. Too much timing is not a good thing, either.

i just upped my timing from 6 to 8. any downside?

Do you hear it pinging? And I usually kept my thirdens around 6*

no did not, however if you are familier with ebl p4 flash, it does register a tiny bit of knock sometimes after i let off after wot... but i think i did that a little at 6 too

Since you are starting the burn earlier in the cycle you will see a slightly leaner reading on a wideband but nothing significant specially with only a 2 degree increase in advance..