When I floor my truck and it down shifts into passin gear a good amount of white smoke comes out of my exhaust. I call it my "smoke screen" b/c after i pass some one they are covered in smoke.[:'(] What would be a cause of this? Also i discovered oil around my spark plugs on the passenger side I think i might have a leaking valve cover what do u ya'll think? Thanks in advance.

 

leaking valve cover will smoke under the hood not the exhaust , valve seats will cause smoke out of the exhaust so will bad ringson a piston, time for a compression test..

 

definately in need of that, also check the plenum, if oil is getting mixed with the fuel I think that would smoke

 

Typically white smoke signals coolant burning though, so if it really is white I'd check to see if you're losing any coolant first.

 

Park it floor it and smell it?

 

+1 You are right.

For smoke coming out the exhaust this is typically the issue:

1) White smoke = coolant
2) Blue smoke = oil
3) Black smoke = fuel

If you are pouring out true white smoke, you're getting engine coolant into the engine cylinder somehow. Possibly a small head gasket leak that doesn't show much except under high RPM's or you've the dreaded cracked head near the valves. Either way it will only continue to get worse.