tach jumps all over when depressing gas pedal

by Barry
(Canaveral Grove )

The tach jumps to zero rpm whenever I step on the gas pedal. I've been having many issues with this car for several weeks, one is the tach another is a lot of black smoke, runs rough throughout all rpm ranges and very poor milage. I have checked many components however I'm thinking this may be the dreaded optispark. Here's a list as to what has been checked and changed: Plugs, wire, injectors, press regulator, charging, water pump, iac valve, egr, map, filters, TB, & tps... there might be more that I forgot about. Also it is down on power considerable, this should be smoke the tires without even trying... it barely spins them

Chris Trautman @ Corvette Assembly Plant 2019

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