Hello, so my car keeps coming up with an EML light, have had an obd scan and comes up with cylinder 1 misfire ( have replaced the spark plugs and have gapped them to spec, also replaced coil plugs) and a fuel trim, bank 1system too lean 

However when I put Tesco's momentum 99 in the light clears off after a day or two, when the car has around 50 miles left in the tank the light comes back on. I have done a compression test and it has a good read with a difference of 10-15 psi 

 

Any one else having this issue or can shed some light ?

You need to do a leak down test in addition to the compression test on number one.