from my post on 350z tech:
finally got around to installing my thermo spacer kit yesterday quick check all good and took for a moderate drive...maybe a little crisper/strong through the rev range, but nothing earth shattering. Got home tonight and re-did the ECU tricks:
1. throttle valve closed reset
2. Accel pedal released learning
3. idle air volume
4. reset ECU (2x last night did not get the timing right, but the check engine doing it fast --> slow flash wiping memory clean tonight.
Car was hot from a 25km commute home, so this time I though gotta try WOT - afterall that's when the short-comings of the old plennum would've been apparent. Wowwee! different car now with my twin 60mm S/S exhaust + 5/16 Thermo plennum spacer kit. Above 5k rpm WOT I sang 'turbo' as it came on song. What hoot, very worthwhile for $280 and 3 hrs careful install. Not a thing out of place with the kit - other than I added couple more washers myself and used 6 of them for the strut brace bolts as the included bolts do not have integrated washers like the OEM bolts.