Has anybody researched the difference between the Calif specific engines and the federal versions? Usually, it used to be that they (Calif) had different cam timing, EGR valve and different catalytic converters so gas mileage was 2-4 MPG worse. It is possible that they now may be just using different cats plus different ECU settings. I am considering buying a 129 with Calif emissions.

 

Firstly I'm not very familiar with the particular model.

From what I can gather Mercedes references suggest they have one broad specification for the "North American market exports" which adheres to Cali emissions, and another for the European market.
In mid-80s cars (which is the design spec the 129 is based on, a 124 floorplan with M103 and M104 base options, only the M119 option and body/features is 90s tech), well there was distinct detuning in North American deliveries. A 280E for example has a "euro spec" or an "american delivery" cam/tuning spec worth about 30hp, both wound up in Australia and the difference is dramatic, my BIL's euro spec is a very quick car able to keep up with local 5.0 V8 contemporaries no problem, an american spec one is a total shopping trolley that feels like any other local six.
In cars like the base spec 190E Mercedes wound up using the Cosworth bore/stroke for the M102 at 2.3 litres to achieve the same power as the Euro 2.0 litre version for the North American market. They didn't offer the 2.3 litre option in Europe until years later (alongside the new 2.6 six option) and it had about 15hp more (but was achieved by tuning refinements so US got this version in 86 too).

What you maybe referring to is the possibility that it is okay to import Euro spec Mercedes cars in states with less strict emissions than Cali, but in Cali they wouldn't pass emissions. But generally if a Mercedes is intended for North American delivery at the factory, as far as I know it adheres to Cali emissions and is detuned if necessary to this effect.

What I suggest is you compare European spec to specification from factory for the North American market as a general rule of thumb. I don't think there was a special "Cali" version plus a regular "North American version" but they are the one version and Euro deliveries another version (Asian deliveries another version again, same fuel spec as Euro versions but lower interior spec usually, cloth instead of leather for tropical regions, etc.).
However according to Wikipedia, in the R129 the high output version (AMG style spec) of the M103 and M104 sixes plus the new M119 V8 were both available in North America with the same spec as the Euro version in early versions, whilst in mid-90s versions the M103 was dropped and the M104 revised in 2.8 litre and 3.2 litre versions (in common with sedan fitments), but the 2.8 litre was not offered in North American deliveries.
This does infer that the six cylinder 1994-1998 US version of the R129 was lower spec than the Euro version.
It appears however than the M119 V8 and M120 V12 versions are the same as the Euro ones.

In any case a ca.1990 M103 six in sedans are same spec for North American deliveries as Euro deliveries, and de-catting them is only worth 5hp at the most anyway, you can restore as much with race filters and plugs.

Best I can do, someone more expert on this particular model is the person to talk to.

edit to add. Oh one thing Mercedes was doing with North American deliveries whether or not they're the same spec as Euro ones, which distinguishes them is they put seals on all the tuning points, like mixture adjustment so that home mechanics can't alter the factory settings without special Mercedes workshop tools to do so. This is a Cali requirement but also to differentiate different fuel grades available in Europe, ie. it is definitely much easier to modify a Mercedes for higher aftermarket performance in Euro versions than in US delivery versions, and more legal to do so. Until recently...new Euro legislation prohibiting aftermarket mods is in the works presently.

 

Thank you for the reply