2018 CX-5 Sudden Misfires in 2 Cylinders on Highway

2018 mazda cx5. 112000 miles

While driving from Wisconsin to Minnesota today my CX5 started running/sounding really rough whenever I accelerated(engine rpms around 2500 at 70 mph). The car would even shudder and vibrate . I pulled off at a rest stop to plug in my diagnostic tool which showed a misfire in cylinders 1 & 3. After I got back into town and stop and go traffic, the car would essentially bellow when I accelerated from a stop and would shudder more but would then sound smoother after getting up to cruising speeds.

Some background:
Last December I started getting really poor mpg and noticed a soft thumping noise like a muffled air compressor pump when the rpms would drop low when shifting to reverse or coming to a stop while in drive. It's since gotten worse and today it was really prominent.
last month I had the adjustable Hydraulic lifters replaced due to lifter ticking noise. This was related to mazda's TSB regarding issues with their cylinder deactivation tech. That issue waa resolved.

I'm not sure if the valve lifters had anything to do with what I'm experiencing now. Thoughts?

Could it be clogged fuel injectors? I've never had them replaced or used any kind of fuel system cleaner. There was one instance last month when I came to a stoplight last month and the rpms dropped to around 600 and then the car shuddered as if it was going to stall
 
Given the significant engine work that was done, you should do a wet/dry compression test asap.
 
Given the significant engine work that was done, you should do a wet/dry compression test asap.
Before replacing the lifters i asked my mechanic to do a compression test. They were all around 195 psi except cylinder 4 which was at 260 psi. That also was the cylinder that had the failed lifter and by my understanding of the Miller cycle engine in the cx5, the intake valves stay open for a time during the compression stroke. Since the lifter failed, one of the valves would've been closed thus causing higher pressure in that cylinder.

I'll admit, I don't know if he did the test after the repair.

If my current issue isn't related to the lifters, what could I expect to learn from the wet/dry compression test?
 
It's not just about the lifters, because lots of engine disassembly/reassembly was done in order to change them. So there are a number of possible failure points, such as improperly torqued bolts loosening up. The simple and easy compression test will either confirm that the engine is mechanically ok, or immediately let you know if there's an issue.
 
How's your spark plugs?
That's my first thought. They're supposed to be changed at 75,000 miles aren't they? A fuel cleaner couldn't hurt or a high quality/detergent fuel. Try the simple stuff first.
 
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