Muffler delete helps mpg?

[CappAttack]

Dear JettaD is now at 235,6xx miles and has been my daily driver since the end of October. Have been reliably been getting 36-38 mpg per tank. From the get go I had a full upper grill block (with a cutout for the air intake port there) and approx 40% lower block, aluminum skid plate (Plate rides approx 3in above the pavement), tires at sidewall pressure (44psi), raodo antenna relocated to inside rear frame between rear pass window and rear window, and a home made CCV filter.

Planning to install a coroplast and/or sheet metal belly pan, get thinner tires that are also LRR rated (mine are almost to the wear marks), get a set of bosio sprint 520 injector nozzles, and an ECU tune from somewhere (Malone maybe? Site says he can do VW TDI specific tunes).

My question is this. Last Thursday I chopped off my muffler and almost immediately my UG started showing an avg mpg of 48-50 instead of my usual 36-38. Have not conciously made changes to my driving style since then and have not made any other changes, still fill up at the same pump from the same station every time. Is this a possible gain from the muffler delete? Or did I do something else incidentally? Anyone have similar experiences with a muffler delete?

[oldtamiyaphile]

I think muffler deletes can pay off in diesels, but keep in mind that any mod probably means you need to recalibrate the UG.

All OBD gauges are pretty much guess-o-meters anyway and especially on diesels.

[oil pan 4]

Yeah it could help. Less back pressure on the turbo will force more air into the engine giving better MPG.
But only on a diesel.

[RedDevil]

Was the muffler clogged?
It could not have had so much effect if not?