New to forum but I've read hundreds of posts so far and I'm excited to get the LR forum input on this one!

1 month ago I started truck and it was fine. 2 miles into drive to work it started shaking and running rough followed by cel and a engine system fault on dash.
Pulled into first auto parts store, code reader said cly3 misfire.
Limped it to my shop (I design,build and maintain electrical systems for Featherlite coaches) I replaced replace the coil and all plugs with no result. I threw a new injector in it with no change.
I had engine running and unplugged each coil pack one at a time and the rough idle stayed no matter what.
Shut truck off, let it sit for 4 hours and it "fixed itself" magically. Fine for 29 days
Two days ago someone pulled out in front of me on the highway and I went 70-20mph real quick and during the acceleration back up to speed I got the shudder and cel and ESF again.
Genetic code reader again said cyl3 misfire.
I dident have time to mess with it so it went to my local import shop (owner has a 2004 disco) he said generic code reader was wrong and it was actually cyl2 had a bad coil and that I needed to put ngk plugs into it. 660$ later it ran good, for approx 6 miles until I had to stop quick again.
Cyl3 misfire on genetic code reader again.
Shop wants to Charge another 110$ to hook back up to their reader but I'm not sure I wanna go back again and I Deff can't afford the dealer chasing this issue.
Please help!