Modern Vespa

I have seen a couple of posts recently on exhaust mods - I have a couple of questions:

On a GT 200, about how much additional top end speed does a performance exhaust produce?

Are there additional modifications required in conjunction with an exhaust modification? (I am thinking things like jetting from my old 50cc scoot)

Does an exhaust mod effect the Warranty? (This will be OBE by the time I get home any way, but I was just wondering)

Thanks in advance for the posts/info.
Coach

I don't think you have to re jet the carb on the scorpion pipe but I'm not sure about the PM pipe. It may void the warranty but you could always put the stock exhaust back on before you take it in for service. I don't think it really increases top speed much. I think it's mostly a cosmetic and sound difference. I really want the PM pipe but good greif it's expensive.

According to Scootering magazine with a GPS on a GT200, top speed with a stock exhaust wa 70mph, and top speed with a PM Tuning pipe was 74mph.

The 150 motors don't seem to need any upjetting. The GT200 seems to need an upjet even from the factory, so it couldn't hurt to do it on an exhaust mod.

Wow. I would have thought it'd higher then that. I've cracked 70 (indicated) on my stock LX150, meaning I was probably a little over 60 actual. Or maybe the "optimistic" speedo is on a hyperbolic curve?

Thanks for the input.

I can hit 74 indicated with the full windscreen on level terrain, but was hoping to add another 5MPH to the top end. If its just sound and cosmetics the exhaust mods add... well, I'm cheap and will probably just leave it stock.