Hope to be clear...

I bought this truck a few months ago. It is a 05 with a 4.6 engine and 2WD.
Since I bought the truck I felt it a little bit low of power or too heavy and could hear a very ocassional rattling but as the truck was stopped for a few months I tought that was because old gasoline, etc...

This rattling was more common when A/C was in use but now I can hear it even with the A/C is not in use. I hear this rattling when I press the gas pedal and it does not matter if I do it hard or not.

Also now the truck has some vibration while in idle. It is very soft but not normal.
I have used a OBD2 scanner and no codes are shown but I did the KOER test and tests 82, 83 and 84 result on a low EGR voltage. Around -4.7.

Do you think that the EGR is causing this ratlling and lost of power?
Coudl be something else?

Some friends say that may be the catalytic converters are bad, others say that could be the spark plugs but truck has 78k miles and as far as I know spark plugs must be changed at 100k.

The mechanic told me that old spark plugs could be causing this and if mine have 5 years on the truck he said that that could be the problem.
And this was his only explanation as he did not find nothing worng.

I have not done to much on the truck. Just replaced the air filter and also check only one spark just to see if they were motor craft as I don´t if previous owner changed them and I have read that other brands do not do a good job on these trucks.

Other guy said that if the truck was running in a diferent altitude and now is almos to sea level that could be the reason.

Now, I´m confused as I espect all sensors in truck detect the problem or do the adjustments if altitude were the problem but I´m having no codes, except for the KOER.

Truck runs fast and everything else is ok but this rattling also the loss of power (or feelling of a too heavy truck) are making me crazy .

I also have 2001 f150, 4.6 and 2WD and this one has more power than my 2005.

Any comment will be appeciated.

Thanks!