it could just be that your old recircs are just worn out after 10+ years and ?? miles. I did have mine replaced when I had my T28's put on just because mine were still original ones and it seemed to be a good idea..I find myself replacing so many failing original parts that now whenever any work is done on my car if there is some other part still original in the same vincinity I just replace it anyway since the labor is already mostly done...saves me money in the long run. I would post in tech forum to see if any nissan techs here know the testing procedure for recircs.
1990 Twin Turbo 5spd "BPU+" No Show,All GO 1999 Maxima SE 5spd
ECZA member #0314
..."If it doesnt make it faster, I dont care"...yellowZXTT