125-200cc Wre 125

Hey i was thinking of buying http://www.ebay.com/itm/FMF-Fatty-Polished-Exhaust-Pipe-Husqvarna-WR125-2000-2001-2002-/261079627672 for my wre 125 mod 2000 And i have a few questions

1.Will this fit with the stock muffler? (can't find a powercore2 for the 2000-2002 mod)
2. i am currently using the stock carb no idea what jet is in the dellorto PHBH 28mm.
3. if i get the fmf exhaust how much should i jet up?

From the 07 manual standart jets sizes

Rif. Part Dell’Orto PHBH 28
1 Throttle valve 55
2 Tapered needle/needle position (notch) D 48/2nd notch (*)
3 Idle diffuser jet U 38
4 Float nr. 2 - 6.5 gr
5 Main jet 142
6 Spray nozzle HN 268
7 Starter group 60
8 Air screw, open by “n” turns 1 e 1/2
– Diffuser diameter mm (in.) 28 (1.10)