Could it be manifold

[Patrick1234]

Hi all, 

I have 09 2l D4D auris for the past two years everything going good but recently I have noticed that the mpg has went down from about 50 to 44mpg (I use the same filling station). I have also noticed that she feels down on power if you floor the throttle.. she is burning a bit of oil but nothing I will worry about.

I recently drove my dad's 07 avensis D4D 2l (240k miles) and she seems to have more power than my auris.. 

I had a friend of with snap on diagnostic tool and he has said that the intake pressure is not normal ( can't remember the Value he gave me as this was when I got the car) he suggested that it was the map sensor and I replaced with little to no improvement.

I have few questions,

1. could there be a crack in manifold- is this common and could I just weld over it?

2. Could in be the gasket?

3. Is there a simple way to check both these? 

Fyi, there are no warning lights for this.. I have also recently cleaned the egr as she was throwing up a code for that which I have sorted.. there was alot of carbon in there for a car at 130k miles.. 

Im avoiding mechanics ATM as I use this car daily and I will try to resolve this myself if it is in fact the manifold/ gasket.

Thanks. P.