[Teddy250R]

who makes a good big bore+porting compatible pipe? i've heard bad stories.
currently have a ptr '98 eliminator pipe on a 87 wondering if it can handle 300+ cc?
and what's the best way to get 300cc straight bore or bore/stroker?
main usage will be sand

thanks for any advice

If you are under or around 300cc's I would say your best bet is a Sparks TT or ESR TRX-5.

Here is a pipe test done by Dave Moore at Dave Moore Racing:

 

[Teddy250R]

Is that graph showing a trx5 standard mount or center mount?

I believe it is the center mount.