well i have a 90 gsx with a jdm motor installed in it.
im having problem with rpm gauge....i know 90 model are the odd one out from the group but i have looked at the wiring and it looks good.
problem is all my gauges work until i hit boost. once i hit boost, my rpm goes to zero.
i have some after market gauges. according to my boost gauge i can sustain 9psi solidly.
what should i do to fix my rpm weirdness under boost?