Rough idle and poor gas millage

Looking for help with my 2001 SR5 4X4. The car recently started averaging bellow 11 mpg. When idle drops to to 500 rpm there is a definite miss.

No codes no check engine light. I have taken it to 2 mechanics. The 1st verified the miss but only suggested running fuel cleaners and high octane for a couple tanks. I've done as suggested with no improvement. The second was at local Toyota dealership. Toyota Tech ran a cylinder leak down test and discovered a 39% leak on cylinder #6. Tech also confirmed the leak is through exhaust valve but not why it's leaking (valve, lifter or something else). After symptoms started but before I took it to the mechanics I changed the timing belt, plugs, oil, fuel filter. I've also replaced all vacuum lines except for the brake booster line and check valve which looks to be in good shape.

I also ran a compression test and saw 150psi in every cylinder.

The car still accelerates fine at part to full throttle.

My question is if the cylinder leak would be enough for the miss at low idle?

Any suggestions for repair or further diagnosis is greatly appreciated

 

One cylinder being a bit down shouldn't make it *that* rough. Like that's not good, but I've had cars that absolutely suck oil through the piston rings and they still don't really run rough. A single mediocre exhaust valve probably wouldn't be that bad either. Some silly things to check, are all your ignition coils good and free of cracks? No oil in your coolant/coolant in your oil, and no overheating issues? Any codes come up at all, ever?