Actually an I30T... Service Ignition soon light came back on after had filters, spark plugs, one bad coil replaced. Car is running fine, no skipping or misfiring cylinders according to scanner; just pops up P1320. I've been told I need to replace all the codes because there is no way to pinpoint or test exactly which coil is bad or just weak by an Infiniti dealership; a parts store clerk told me that the connectors or boots from coil to ignition should be tested first because that could be the problem; Emissions tells me it could be the ignition primary cable which Infiniti dealer tells me doesn't exist...each individual coil has its own separate connector/boot. I've already spent about $500 to remedy this problem and would like to get it rectified as I am due to take the car through Emissions within the next 33 ys. I'd rather not have it fail emissions before my mechanic resolves the issue. Anyone out there have a similar problem and had it fixed? If so, what was causing the problem?