fuel consumption higher than average, and LTFT are slightly higher

Hi Folks, 
I have a Lexus GX460 v8, 2ur-FE engine code, with just below 84,000miles. The car is a 2011 model, with 1 inch lift and 265 tyres, it has the slimmest and lightest roof tent on the market. 

Lately I have noticed the fuel consumption was reading higher on the dash tripcomputer, it is reading 11mpg, when the fuelly average is 14-16mpg, maybe mine would be 16 or 17 due to the mods. 

I have plugged in the toyota techstream, and at idle, warmed up engine, no AC/Lights etc, the LTFT is sitting at B1 9.4% and B2 at 3.7%, stft is oscillating betwene -4 too +4, the O2 sensors are around 0.8-0.7V on both banks. 

Then the strangest thing, just a slight press on the throttle, i.e. going from 700 rpm idle to 800rpm causes the LTFT to change immediately to B1 11.7-12.4 and B27-8

I have done a smoke test with cigar, no results, and also the propane test, and no results found. 

The car has had the intake opened up to fix a coolant leak in the valley plate. I do note that the connection from PCV too intake is oily, and I dont have the needle nose pliers to remove it to check if stuck open, but will be doing that. 

Currently there are no codes, and no CEL as the LTFT is still low, but definetly something is not right due to the fuel consumption. 

 

Those trims aren't that bad. Considering they actually went slightly more positive with higher rpm makes me think you will not a vacuum leak.
You can try cleaning the MAF to see if there is any improvement in trim, but in all honesty, I think your thirteen year old V8 SUV just probably doesn't get stellar mileage.

Sorry I should have mentioned, that I have cleaned the MAF.

Would a blocked PCV valve cause these kind of readings, and what is really throwing me off is the rate of change of LTFT, I always thought it is gradual, not instant. I am literally just tapping the throttle, and the LTFT changes.

  The instantaneous change in LTFT is perfectly normal. The PCM watches multiple inputs and creates (I should say modifies) the fuel trim map, which has many cells, or blocks. Each cell has predetermined or learned trim values. When you snap the throttle, as the engine warms up, as loads are applied, the PCM picks the appropriate cell from the map that all ready has the LTFT value determined.
So you're just seeing the map change from the "idle" cell, to the "touching the gas pedal in neutral" cell.