mine came with a o2a from stock.but short geared so i swaped to a cyp and that make all the difference.
i have a 1.9 idi and with the cyp gearbox its all that some can ask for (in normal use.)
its intercooled(front mount),proper oil cooling system,vnt 20 and custom intake manifold.
most of the IDI“s problems were solved there.
did a 650km trip with speeds around 160 going to there and 180 comming home and it still averaged 6.8l/100km!
thats in a 35i wagon,dragging heavy widened steelies and 5 people inside so i am pretty happy and say no to people that say only tdi“s are the way to go to achieve that...
my modified aaz in an mk2 is 2-3 times faster than the 1.9alh tdi in a mk4 as far as my butt can tell. BUT that was a massively worked on AAZ with lots of fuel, dynamic timing advance, no gov., FMIC, 2.5" open exhaust, lots of porting, T03 Garett @ 26lbs.
The biggest advantage I see with TDI's is the ability to run propane and NO2 without much concern. (again the benefit of no pre-chambers as mentioned earlier). The AAZ is easier to work on for sure and much cheaper.
I got 50mpg casual driving and melted the tires driving it like i stole it. Never saw higher than 1,200F EGT. I dont know what the TDI's typically do stock with that VNT in it.
my modified aaz in an mk2 is 2-3 times faster than the 1.9alh tdi in a mk4 as far as my butt can tell.
You can't even compare a beefed AAZ to a stock ALH. However, a tune and injectors on that ALH would sure change your mind
. No other work needed then that and you make some serious power. Reliably all day long. That's really where the advantages come in with the TDI (not necessarily saying the Direct Injection) just the next gen VW diesel engines. Specifically the ALH, it was built to withstand 3.5-4x more than what it produced stock.. with factory components. That is what makes them better in my eyes.
That is something else that should be mentioned is how much the different nozzles effect performance on tdi, which is nice I am guess this is because there is no swirl chamber
The stock nozzles are undersized and are only capable of stock fueling. They are not like the idi nozzle where stock they are 50hp but those same injectors will glow 225hp of fuel.