How can I get 2004 Frontier P0400, 0430 and 0171 code related problem advice..

What is your question?

2004 Nissan Frontier 3.3LSOHC engine, automatic transmission, 4wd 76K miles. I have a lengthy written problem / repair attempts background and lengthy list of related detailed questions, These are too large to cut and paste here. I there a alternate means to send this background info and detailed question list to you for evaluation and if found acceptable rough answer and advice cost estimating ?

What makes this problem better or worse?

After May tune-up Idle is rougher. Accleration, 70 mph operation is better.

How long has your 2004 Nissan Frontier had this problem?

Since 7 May tune-up, valve cover gasket replacement