HFC's. Stillen or Berk???
 

I thought I'd ask the question.
Which one ones would you buy if you were keeping the rest of the exhaust system stock.

Probably the Berks. A lot of people have them and have had great success with them.

^^ i agree i'd go with Berk also.

Berk, because it has an extended O2 port the Stillen doesn't. Plus you don't need to worry about re-using the stock o-ring on the stock cats.

Berks line up to everything so nice too! I love my berks

the stock cat doesn't use an extended O2 port. Having a long tube makes me think the O2 sensor would give an inaccurate reading because hardly any fresh exhaust gas is moving by the sensor. What is the logic behind using a long O2 sensor tube?

The same logic as using anti-foulers with test pipes (which close off the O2 sensor from the exhaust entirely, btw). The extended tubes are basically built-in anti-foulers. Also, keep in mind that there are O2 sensors in the headers, and that's where the functional data is being gathered from. The sensors in the cats are just there to make sure the gasses that have passed through the cats aren't 'too dirty', so when you go with test pipes especially (HFCs to a lesser extent), giving those secondary sensors an inaccurate reading is actually a good thing. In other words, you want to 'trick' those sensors into not sensing the dirtier exhaust gasses. Again, not so much a concern with HFCs as with test pipes, because with HFCs, they're still cats. But with test pipes, you're not filtering the exhaust at all, so you definitely want to shield the sensors. I ran test pipes in my 350 and within a couple of days it started throwing CELs. I'd reset it, and it'd just come back. So I finally broke down and installed anti-foulers to segregate the secondary O2 sensors from the exhaust completely.

One other thing I forgot to mention is that the Berks have built in ports for wideband O2 sensors, and the Stillens don't.

I've got the Stillen HFC and CBE (and G3) and it sounds fantastic - even better than I thought it would. No rasp or install issues and I like having all the same manufacture parts as well. I was worried it wouldn't be throaty enough but it sounds really mean and agressive. Finally my car sounds like it looks and the extra HP doesn't hurt either! :)

Any problem with engine warning lights with either of these HFCs installed?

I've had no CELs with the Berks.

Our HFC's are true 2.5" for maximum flow... We have seen other companies HFC's reduce to 2.25" or smaller

Just installed my Berks race pipes yesterday and everything went great!! perrrrrfect fitment and everything.:tup:
My CEL came on at the end of my 2hr drive home from the shop that installed them.. which i dont care about as long as it doesnt cause any problems.

Once again :tiphat: to BERK!

I was debating test pipes but I ended up going with the Stillen HFC and CBE and now I don't have to worry about the CEL ;)

Our HFC's include cel fixes so you don't have to worry about a CEL.