My a15 has got twin 40mm dollortos, miled head work, a slightly lumpyer cam, GX header's and an about 1 3/4" system. and it pushes all 700kg's of a 1200 along pritty quick. and with it grandmar spec exteria right down to 12"+hubcap's it's wiped a few smiles of face's p.s. Make's the wickedest noise when the secondarie's do there thing from about 3000rpm's all the way to about 7250rpm's and it pop's like f**k when you make re-entry,