I have only had the 78 280z for a couple

of weeks. (stock L28 motor-fuel inj.-5 speed)

weeks.

It has a noticable ping.

Slight smoke at idle.

Smokes like a freight trane when you stomp the gas while driving.

It is white smoke witch I thought was oil but it has a VERY strong smell of gas.

Has a slight backfire on fast decel.

I did a compression test today.

pumped up between 175 and 180 on each cylinder, but leaked down pretty quick.

I took her out and really romped on it today.......motor feels like it is pulling strong until 4th gear ...at that point speedo would not go past 80 and you could hear slight pinging.

What do I need to look at.....any idea what the problem may be?

to me it sounds like you are running absolutely full out rich. first thing i would check is the cold start and the afm.

running that rich i cant see how you would have detonation though.

pull your plugs and see what they tell you they should be black and fuel fouled if im right

oil smoke is blue unless mixed with a too rich mixture of fuel then it will be black unless you are running a cat.