Got my turbo build up and running on a basemap (woo)

couple of issues have occurred since the build which wasn’t present when NA but on standalone w/wideband.

my tach jumps about around 800-1100rpm
tunerstudio doesn’t reflect this and it says a pretty solid 870-900.

also my iacv is buzzing audiably.

the iacv frequency is 180mhz (pretty sure this hasn’t been changed from being N/a)

cars a 1994 NA8 so tach isn’t controlled by the ecu, the cars been sat for a month or so a failure in the clocks is plausible but unlikely.

Iv fitted a Mac EBC, could this be causing interference?

i may try cranking up the iacv frequency to 500hz

thanks for any ideas