I was using a freescale pressure sensor that measures pressure with respect to ambient. With a channel immediately upstream and a channel immediately downstream of the IC I bet you could get a fair idea of the pressure drop. I can also program it to take averages, peaks, or even make it do some limited logging over a serial link.

LI-S4 and I tested on his car in parallel with his analog boost gauge and it seemed to track pretty well. I performed subsequent VAGCOM logging of boost on my car with similar results

What do you think? Should I dust off my prototype?

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2002 Nogaro 6spd S4 with Sport Package
click here for my photo albulm

-Neuspeed RS10's with 235/35/19 Bridgestone RE050 Pole Positions (summer)
-RS4 Replicas with 225/40/18 Dunlop Wintersport 3Ds (winter)
-Stasis Motorsports with 700F/800R springs, corner balanced
-Intrax front sway bar, Intrax 22mm rear sway bar
-EPL stage 3 custom tune :)
-K16/K04 Buehn Engineering hybrid turbos with ceramic coating, port and polishing, and turbine clearancing
-AWE Intercoolers, Twin2, DTS
-ASP 3" downpipes w/cats
-VAST ceramic coated exhaust manifolds
-Clutchmasters Stage 4 clutch and lightweight flywheel
-Stasis high bias 4:1 center differential
-Stasis Motorsport 14" 6-pot Alcon BBK
-Stasis Tracksport rear brake kit
-RS4 motor mounts, RS4 tranny mounts, VAST snub mount
-RS4 grill, M3 lip spoiler, Euro tail lights, XM Radio
-APR bi-pipe
-710N BPVs, Walbro fuel pump, Samco IC hoses
-Toyguy shifter
-otherwise BONESTOCK...

Been there, done that:
-CPP front upper control arms (RIP after 20K)
-Meyle "OEM" upper control arms (RIP after 17K)
-Tracksports with 600F/700R/touring valving
-Tracksports with 700F/800R/sport valving
-Tracksports with 550F/650R/sport valving

Interesting Trivia:
-Clutchmasters flywheel weighs 13.95lbs.