I "got into this" years ago with both iPd and TME (swede makers of ecu).

iPd said exhaust upgrade was unnecessary.

[The] TME guy basically said I'd have to be either ignorant, insane, or both to
run the ecu w/o the exhaust upgrade.

My take on this is that, apparently, with relatively low U.S. speed limits, the
system can handle the increased engine output, provided you don't use too much of
it too often. But you can also easily melt oxygen sensor(s) and/or catalyst (plus
cause other stresses) if you spend too much time in fire-breathing mode.

I latched onto a 'skunkworks' ecu with fattened-up (bump in mid-range) torque/boost
curve and kept the stock exhaust. The Bosch Platinum plugs deal with higher temps
like magic, and there have been no problems that resulted from the moderately
increased performance.

- Dave; '95 854T, 131K mi