Advance timing refers to the ignition timing. When you advance, it lets the spark burn sooner than the time it takes the piston to get to TDC, thus having a longer burn, more combustion, more power. The only downside is knock. So to compensate for knock, you have to run higher octane fuel. But the process of doing this correctly involves messing with the TPS sensor which can result with incorrect idle speed. The service manual should indicate the degree tolerance specs of the ignition timing, shouldn't be no more than 1 or 2 degrees. So the only benefit from this is a very slight increase of throttle response, so it won't do wonders. And at the expense of risking engine damage in terms of knock and pinging and spending more on higher octane, its not a good mod.
How do you even advance the timing? I know in older cars you can just rotate the distributor a bit. Stock is usually about 15 degree and people would bump it up to 17 in the 240's and other older nissans. Usually neeed to run higher ocatane fuel to prevent knocking. On a V with no distributor how do you even do it?
This was done on my 240 but I didn't notice enough of a hp gain. Not something I would bother messing with again.