[b]IronCross:

The two 56s and 72s were each one early, and one late. Even though you bought all four on the same day. The cylindric mufflers were all replaced by the cast ones on the mid and big block engines.

I have always classed the 10mm exhaust as small block, the 12mm as mid block, and of course the 14mm as the big block. Saito seems to follow this also, but I was mistaken about the 56. I thought it also had the 12mm exhaust. Memory fault.

Coveredup:

Back pressure differences will affect a 4s engine, but the effect is mostly in the lower/higher muffler pressure. Higher back pressure=higher fuel pressure=easier consistent engine run.

All:

Here's a picture of five totally different exhausts, all supplied at one time or another from the factory with Saito engines. And there are more not included. All from the factory.

Bill.