P1128 & P1130 (Again)
 

First I did search and found some answers - tried solutions but did not help.
When the car is cold, the engine runs rough for a few minutes then smoothes out.
The p1128 and p1130 codes trigger if the car is in traffic sitting (idle) for an extended period of time.
Car still runs great!
I cleaned the MAF - no difference
I have swapped the MAF - made no difference.
Replaced AOS.
Replaced cracked dip stick tube.
Replaced both pre-cat O2 sensors.
Checked Intake connections - everything is tight.
As per my OBDII Reader, one O2 sensor reads a little higher than the rest.
Any other ideas or suggestions?

Which o2 sensor is reading high and is it within range? If not try replacing that sensor (unless already replaced, not clear). You may also try running a bottle of chevron tech Ron through. I did this along with an o2 sensor replacement and my car hasn't popped these codes since.

It's not the 02 sensors, they are reading like they should. You have a lean condition caused by false air introduced after the MAF, so not measured by the MAF. The ECU can no longer keep the mixture in range by trimming so throws a code.

1128 and 30 are the idle mixture trim code and not running at speed codes for BOTH sides of the engine. I would concentrate my looking at the center of the plenum for a cracked rubber part of loose clamp. The other thing to change is the fuel pressure regulator on the drivers side of the engine. It's a $45 part and 15 minutes to change.

Chasing these leaks can make you pull your hair out!!!

I was reading that "lean" condition on those codes only apply to 98 - 99 cars? On later cars it indicates a "rich" condition? Can anyone confirm this?

Ever so slight a vacuum will throw these codes. Check all your hoses including AOS and slip connectors. Mine was the corrugated Aos at TB after 996 conversion.

These codes can also come from a dirty or out of spec fuel spray from an injector. The techron can clean them and take care of that. Being that you've taken care of a lot of the primary causes for these codes, try a fuel cleaner.

I will give the fuel cleaner a try. Is Techron what most people here are using?

I use the Lucas fuel system cleaner. It is also MUCH easier to get into the fuel fill flapper valve without spilling.

Techron came with the most wide recommendations. Make sure you get the size that treats over 12 gallons.

Vacuum leak somewhere. Check the MAF values. For the base it should show 13-15 kg/min. If its less ghan that. You have vacuum leak.

Agree an intake air leak is most likely. A failed MAF is also possible as the car is running lean. Clogged injectors are possible but unlikely affecting both banks.

TS guide for 2002 model 986:

DME 7.2 (2000-2002 Boxsters)
P-Code Bank RPM Range Reason Look for:
P1128 1 Idle Engine is running very lean and the fuel adaptation has
pegged its rich correction.
Intake/Exhaust system leaks; MAF not performing correctly; fuel
delivery components cannot deliver enough fuel.
P1130 2 Idle Engine is running very lean and the fuel adaptation has
pegged its rich correction.
Intake/Exhaust system leaks; MAF not performing correctly; fuel
delivery components cannot deliver enough fuel.
P1126 1 Lower Load
(Low RPMs)
Engine is running very lean and the fuel adaptation has
pegged its rich correction.
Intake/Exhaust system leaks; MAF not performing correctly; fuel
delivery components cannot deliver enough fuel.
P1133 2 Lower Load
(Low RPMs)
Engine is running very lean and the fuel adaptation has
pegged its rich correction.
Intake/Exhaust system leaks; MAF not performing correctly; fuel
delivery components cannot deliver enough fuel.
P1125 1 Upper Load
(High RPMs)
Engine is running very lean and the fuel adaptation has
pegged its rich correction.
Intake/Exhaust system leaks; MAF not performing correctly; fuel
delivery components cannot deliver enough fuel.
P1132 2 Upper Load
(High RPMs)
Engine is running very lean and the fuel adaptation has
pegged its rich correction.
Intake/Exhaust system leaks; MAF not performing correctly; fuel
delivery components cannot deliver enough fuel.

This is what I know from hooking up my scan tool (at idle):
1) Both Pre-Cat O2 Sensors fluctuate up and down.
2) Both Post Cat O2 Sensors steady around 0.735
3) MAF reading 3.5-4.0 g/s
4) Pulled Oil Fill Cap, and idle became very bad and there definitely was vacuum present.

The MAF spec above says 13-15 kg/min, should that be kg/hr?
If I do the conversion it is in the ball park 12.6 - 14.4 kg/hr.

Still have not put in the Techron.

You may need to smoke the engine to find the leak(s). You can make one easy enough or take it to a shop that has a smoke machine.