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I believe it is your ignition control module. I've seen many of these causing misfires on the ecotech engines and replacing them makes the misfire go away. Assuming it is the Ignition control module here are the instructions for replacing it.
Ignition Coil Housing Replacement Removal Procedure
Tighten Tighten the retaining bolts to 10 N·m (89 lb in).
Ignition Control Module Replacement Removal Procedure
Important: Make sure the interconnect and seal are lined up before module installation.
Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
Tighten Tighten the retaining screws to 1.5 N·m (13 lb in).
Tighten Tighten the retaining screws to 10 N·m (18 lb in).
Please reply if you have any questions.
Hello hubala, look really carefully for an intake vacuum leak and also check circuits 423 and 406 IC timing control for poor connection on either end at the pcm or ignition control module. Also check these circuits for a intermittent short to ground, they may short on the AC lines near the AC compressor, on the transmission mount, or on the transmission lines where the lines enter the transmission. Here is a schematic of the circuit just click here. Please reply.
Here is another schematic unfortunately it will come up very large on your screen but you will be able to navigate to see the circuits I'm talking about.