These days the polishing of inlet ports is generally regarded as at best of no benefit and at worst detrimental. Porting however can produce a slight gain but only in conjunction with all the other stuff as already mentioned..
Cheers mate, can u really get an extra 10 bhp from a new exhaust and air filter???
I'd like to keep it sounding pertty much the same if pos! NOT like a rally car
The cat robs around 8-10 bhp on a ph1 2.0TS, the cheapest way to get it back is to de-cat, you can buy a de-cat pipe from cybox on ebay, if you keep the front box (first one after the cat) the system is not at all loud, if you remove it its VERY LOUD!, the front box isn't restrictive so best to keep it.
but have they though?....how many have actually done so?...and are they still claiming no long term problems...certainly peeps who know about these engines, you know the ones, the ones who actually work on them don't seem to recommend it, at least for normal road use...extra vibration etc is detrimental in the long term...
and what I can never get my head round if it's so bad then why do Alfa bother fitting them in the first place..all that R&D..what a waste of time and money....
It certainly makes them smoother, but at the expense of a bit of free revving nature.
Are these engines really that susceptible to a bit of secondary vibration? Every other 4 cylinder on the road seems to manage quite happily, including the FIATs from which the block and crank is derived... Regarding R&D... why did Alfa bother fitting twin spark heads? All that time and money, only to go and dump them when the JTS came along?