Just read this, not sure how reducing back pressure will 'muck everything up'. The MAF and the MAP simply see an increase in the amount of oxygen present in the system, and fuel accordingly, and unless the increase in boost is 'well off the chart' (literally and proverbially), will not have a problem with it.
Removing, or reducing the back pressure on the system can only really have benefits, and unless someone can present a paper which concludes that it will have detrimental effects (only benefit I have found is that by allowing more exhaust gas to remain in the cylinders, it reduces NOx!) I can only conclude that reducing back pressure will be a benefit, remember, if car manufacturers don't have
to fit DPFs by law, they avoid fitting them, same for EGRs:
Engine Exhaust Back Pressure
Increased exhaust pressure can have a number of effects on the diesel engine, as follows:
Increased pumping work
Reduced intake manifold boost pressure
Cylinder scavenging and combustion effects
At increased back pressure levels, the engine has to compress the exhaust gases to a higher pressure which involves additional mechanical work and/or less energy extracted by the exhaust turbine which can affect intake manifold boost pressure. This can lead to an increase in fuel consumption, PM and CO emissions and exhaust temperature. The increased exhaust temperature can result in overheating of exhaust valves and the turbine. An increase in NOx emissions is also possible due to the increase of engine load.
Other effects on diesel combustion are possible, but depend on the type of engine. Increased back pressure may affect the performance of the turbocharger, causing changes in the air-to-fuel ratio—usually enrichment—which may be a source of emissions and engine performance problems. The magnitude of the effect depends on the type of the charge air systems. Increased exhaust pressure may also prevent some exhaust gases from leaving the cylinder (especially in naturally aspirated engines), creating an internal exhaust gas recirculation (EGR) responsible for some NOx reduction. Slight NOx reductions reported with some DPF systems, usually limited to 2-3% percent, are possibly explained by this effect.
Turbochargers typically use engine lubricating oil as their lubricating and cooling medium. Excessive exhaust pressures can increase the likelihood of failure of turbocharger seals, resulting in oil leakage into the exhaust system. In systems with catalytic DPFs or other catalysts, such oil leak can also result in the catalyst deactivation by phosphorus and/or other catalyst poisons present in the oil.
Just found this too, admittedly it is with Audi's (not sure how their DPF system works, probably similar, if not identical), however, they removed a DPF, with no remap, and got the following improvement ( 175bhp and 247lb/ft to 187.5bhp and 258.1lb/ft).
( they also then remaped it to 223.4bhp and 334.8lb/ft)
Graph showing improvement solely by DPF removal: