On the 400V, I found that the NGK GPower plugs ignite better especially since the stock condition is a bit rich. Though the GPowers are cheaper the finer tip really helps and they seem to last well too cos they're platinum tipped. They only go up to CR8Es though, not C9E as in the original stock which is a colder plug. but in our part of d world where it's always hot the cr8's work fine.
You might want to check out the crossover equalization mod on the 250/400 FAQs board too.
One thing I'd like 2 share too is old ducati pipes (round section ones)respond gr8 to the V. although a dyno read isn't in order the Suzuki factory guys here really liked the response after tuning it. but try not to use premium gas on the v, based on exp. Other than that u should be happy to find that u get more out of that old V than d 96 up models. so share d pics of chicks sprawled on d bike. Taking d meters out helps em lean over d tank better (: so "getting pumped" on a bike could go well for a passenger too.