Have u done it yet, just do it amaze yourself i can't really say what it will do but it is much better than stock. Look on the Just KDX web site and it will tell you exactly how to cut it open. if you don't want to buy a PC pipe or a FMF fatty they both can't be over $200 if i were you i would just buy a pipe, cutting a pipe a part is tough if you mess up there goes your pipe. I have done this mod, true i have An 01 220 but i wanted to know if i would get any performance out of the stock pipe all i got was noise. You may get some performance out of yours.
PC pipe from Rocky Mountian MC 178.99
FMF Fatty pipe from Dennis KIrk 189.99
Not all dealers are going to carry pipes form 89-94
Good luck hope this helps.