most confusing engine EVER!!!

[SLiguykyle]

KA24DE '96

so i ran my car on the dyno a few days ago in class, and found out that it's running REALLY REALLY LEAN around the 1700 rpm range. we're talkin' 16.33:1 A/F ratios here according to lambda(lambda reading of 1.034).. the higher RPM one (2800rpm) was so perfect it was unbelievable. anyone have an idea what could cause the low end to lean out like that? I'll be taking it back in and we're gonna diagnose it to see whats up. even the instructor was trippin' out at it. any tips on where to look would be appreciated.

[youngun21a]

List your Mods for starters..any Codes..

[SLiguykyle]

no codes, only mods are injen CAI (but has a pretty dirty K&N filter on it), buddy club spec II exhaust, calsonic hi-flow cat, NGK sparks (dont know heat range, they were already on the car) that's pretty much it in way of power bolt-ons