Henstepper

Just a follow up from the fuel burning issue i have been experiencing, i took my car down to supercheap and had them run a diagnostic scan and it's thrown numerous codes Fault memory has P0300, P0302, P0304 all unknown error codes. From what I have read they are cylinder misfires however no check engine light is present. Would these be old faults that were stored in the computer memory? There is also ABS fault c1201, c1231, c0365 but again no ABS light on the dash, It comes on at start up but goes away. Any ideas what is going on?

It was the ecotec v6 3800

I forget to mention my used 09 Aurion seems to be using a lot of fuel. I had a v6 commodore before this car and didnt go through fuel as quick. I know the aurion has a bigger engine and fuel tank but is it normal to fill it full and almost immediately see the guage drop driving down the road?

I bought a used 09 Aurion atx 140k on the clock. The car feels like its bouncy when driving. I took it to the mechanic he said struts are fine. What could be causing the bounce feeling? Tyres look good and have a 41PSI Pressure.