Deck the head as much as possible, thin hg, stock springs will make more hp than stiffer as long as they last, good port on the exhaust side, full exhaust, no air filter, all short stacks, secondary shaft & flies removed, 520 chain, ceramic bearings, swb, best fuel you can get maybe high 180's/low 190's. It's also very dependent on dyno.
the more you deck the head, the less ptv clearance you'll get, the higher numbers you will have to run cam wise and with race cam and 12.5k rpm rev limit or even 13k rpm rev limit of 3rd gen your hp will peak way past rev limit so you will lose power and gain nothing. Get with a builder and go from there, more sometimes means less. For big bore and short stroke 998cc will need rpms to make more power, higher rpm's will need better parts, I think stock pistons/rods should be ok till 14k rpm or so, so whatever power you can get at that rpm will be your limit. With race gas, proper head/cam combo I think 200hp is possible................but it will cost you.
+25 hp from stock ( regardless of the number) is pretty close to the limit I think in most cases.
+20-25 is what I've seen on my 3d gen with full exhaust kit ECU( +1000 rpms rev limiter) head porting-thin hg and high lift cams.With MR9 gas I could have gone to +30 easily ( I've repeatedly seen 4-5% gains with MR9 fuel).
when you go with bigger cams stock pistons put a definate limit to so many things,like cam degreeing,how much can you deck the head etc...