I have also heard that people say the EGR delete/block is what causes the stronger smell. Any truth or opinions on it?
EGR recirculates the exhaust back into the engine to recirculate it, that's what the R in EGR stands for, recirculate. If it isn't recirculated then it comes straight out giving you a stronger odor as CarolinaHD said.
From wikipedia....
In diesel engines
In modern
diesel engines, the EGR gas is cooled with a
heat exchanger to allow the introduction of a greater mass of recirculated gas. Unlike
SI engines, diesels are not limited by the need for a contiguous flamefront; furthermore, since diesels always operate with excess air, they benefit from EGR rates as high as 50% (at idle, when there is otherwise a large excess of air) in controlling NOx emissions. Exhaust recirculated back into the cylinder can increase engine wear as carbon particulate wash past the rings and into the oil.
[6]
Since diesel engines are unthrottled, EGR does not lower throttling losses in the way that it does for SI engines. Exhaust gas—largely nitrogen,
carbon dioxide, and water vapor—has a higher
specific heat than air, so it still serves to lower peak combustion temperatures. However, adding EGR to a diesel reduces the specific heat ratio of the combustion gases in the
power stroke. This reduces the amount of power that can be extracted by the piston. EGR also tends to reduce the amount of fuel burned in the power stroke. This is evident by the increase in particulate emissions that corresponds to an increase in EGR.
[7] [8]
Particulate matter (mainly carbon) that is not burned in the power stroke is wasted energy. Stricter regulations on particulate matter (PM) call for further emission controls to be introduced to compensate for the PM emissions increase caused by EGR. The most common is a
diesel particulate filter in the exhaust system which cleans the exhaust but causes a constant minor reduction in fuel efficiency due to the back pressure created. The nitrogen dioxide component of NOx emissions is the primary oxidizer of the soot caught in the DPF at normal operating temperatures. This process is known as passive regeneration. Increasing EGR rates cause passive regeneration to be less effective at managing the PM loading in the DPF. This necessitates periodic active regeneration of the DPF by burning diesel fuel in the oxidation catalyst in order to significantly increase exhaust gas temperatures through the DPF to the point where PM is quickly burned by the residual oxygen in the exhaust.
By feeding the lower oxygen exhaust gas into the intake, diesel EGR systems lower combustion temperature, reducing emissions of NOx. This makes combustion less efficient, compromising economy and power. The normally "dry" intake system of a diesel engine is now subject to fouling from soot, unburned fuel and oil in the EGR bleed, which has little effect on airflow. However, when combined with oil vapor from a
PCV system, can cause buildup of sticky tar in the intake manifold and valves. It can also cause problems with components such as
swirl flaps, where fitted. Diesel EGR also increases soot production, though this was masked in the US by the simultaneous introduction of
diesel particulate filters.
[9] EGR systems can also add abrasive contaminants and increase engine oil acidity, which in turn can reduce engine longevity.
[10]
Though engine manufacturers have refused to release details of the effect of EGR on fuel economy, the EPA regulations of 2002 that led to the introduction of cooled EGR were associated with a 3% drop in engine efficiency, bucking a trend of a .5% a year increase.
[11]