Yes they are all unique to the various Syncro models
90 bhp RHD GU is p/n 027 253 031AM –
Available at http://www.vw-classicparts.de/bestand/ 027 253 031 A Abgaskruemmer Original Teil 243.30 €
90 bhp LHD GX & 1P is p/n 027 2530 31BS
90 bhp LHD GU is p/n 055 253 031S
160 bhp LHD is p/n (both Rallye & Passat 35i Syncro) p/n 037 253 031AD