I struggled with this issue too for about 10K miles and never was able to get it to run right no matter what parts I changed. Finally fixed it yesterday when I traded it in on a Lexus . . . that's how I fixed my problem.

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2010 Lexus RX350 still new
2003 BMW X5 3.0i w/sport package w/68K miles. (gone Thank God!)
2002 Dodge Ram 2500 4X4 cummins diesel w/198K miles, custom repo truck
2009 Scion tC w/46K miles
2007 Suzuki SV650 custom streetfighter
2000 Lexus GS400 w/165K miles