I called maxium rpm and left a message I haven't heard back from him yet. Is there anything I can do to improve the header pipe or do I have to buy oneIf you only got the slip on hmf exhaust.. that does not remove the major restriction at the head pipe and will likely provide no performance increase.
I tried calling them and no answer or Reply back from my messages I left on his answering machineMaximumrpm.com for ds90 and ds90x performance parts.