Lots O'Codes HELP!!!

[tbonziron]

Hello, I'm new to this forum and seeing as I own 2 Caddys (91 Deville & 97 Deville) I am running into some serrvice issues that the "PROS" want to charge an arm and a leg for. I have 16 years experience in GM dealerships in parts departments so a general understanding is apparent. My 97 Deville has some codes in the OBDII system I can't nail down, now, I never checked these codes before, and yesterday my wife had her brother work on the car at a Lexus dealer he works at. (yeah I know)

The codes I pulled are P0171, P0174, P0300, P0603, P1520 and P1527. I know 0171 & 0174 are lean banks 1 & 2, 0300 is misfire detected, 1520 & 1527 are trans related BUT. WHAT DOES IT ALL MEAN MAN!!!!!! I'M GOING MAD!! I find NIL on the net and dealers are protecting some inner sanctum code of non-information. The Bro-inlaw replaced plugs & wires and the car runs worse than before, rough idle, surging on accel. Cleared codes twice but they KEEP COMIN BACK TIME AFTER TIME!!!

[tbonziron]

Hello again,
NEVERMIND!!! I should ALWAYS, ALWAYS, ALWAYS consult my "IDIOT FACTOR" instincts when it comes to mechanicals and my brother-in-law. After popping the hood and removing the top cover just to have a look see, I happened upon an orphaned vacuum port to the throttle body, hmmmmm "that's queer" I thought suspiciously. At which time I connected the mating rubber hose. THEN...I thought "Mightst I peer to observe the correct routing of the plug wires?" "naw these guys are PROFESSIONALS, But....the vacuum line HMMMMM" so I peered did I, and to my amazement cylinders 4 & 8 were reversed, NOW HOW CAN YOU SCREW THIS UP< THE COILS ARE MARKED WITH THE CYLINDER NUMBER AND THE HEADS ARE EMBOSSED. Needless to say after reconciling these issues and clearing the codes, my baby runs PERFECT!!! NO CODES. Thanks to anybody who WASTED time on this thread.