I just finish replacing the entire Engine valve cover gasket RH&LH, spark plugs and coilcoils because I found excess of oil inside cylinder 1 and 3 and that's why the engine light was doing a misfire.Two day's later the, check engine light came up again with misfire codes (p0303 p0300) same cylinders with the problem. When I remove the coils (1,3) they where full off oil. Any idea where the oil could be. filtering from??

 

Probably the covers themselves and not the gaskets

 

Its bad valve covers. The gasket just prevents leaks to the outside of the motor. The seals attached to the covers for each individual spark plug is what is bad. Normal repair is to replace the valve covers.There is a DIY where you can replace each individual seal if you are tech savvy.

 

If you're going to replace individual spark plug well seals I recommend using a drill press and making a jig to hold the valve cover in place so it doesn't torque around when the hole saw bites. Trying to do it by hand is probably just going to make a mess and maybe ruin the valve cover. Tape off the baffles completely with masking tape so you don't get little shavings and chips of material in them. It's not HARD but it is time consuming but you will save about $350 since the plug well gasket kit is only about $25.

Some folks have also had luck simply using ultra grey permatex on top of the existing gasket, put the gasket material on nice and even and let it sit for a couple hours until it kicks (starts to set up) apply just a tiny thin layer again on top of it before you set the valve cover back on the engine. Obviously it needs to be THOROUGHLY cleaned of all oil residue before you try this or it's not going to work.