Stocky fg turbo,any gains putting on a 3.1/2 inch dump and hi flow cat turbo back to original?

There would be no benefit without a tune to suit (unless you consider the sound upgrade as a benefit). Also, don't change the catalytic convertor without a tune. You can change the cat-back just for sound, if you want. But if you're just changing for sound, then changing either the middle muffler (or remove it) or changing the rear muffler will be enough to get a reasonable sound increase without going overboard.

whats your plans with the car

 

a bit more info mate geezus

My stock BA definitely comes on boost better with an improved exhaust (3 inch cat into twin 2.5). In my view that is an improvement. As Keith is getting at though, your tune is still targetting a set boost level so peak power won't be any better.

What you want to avoid is making it so easy for the turbo to spin up that it boosts beyond what the ECU seems deems is acceptable based on the stock tune. That will throw an engine light and shut down your fun.

Mine hasn't done that, but I reckon I'm cutting it close and am planning to tune it and increase target boost. The BA turbo is different to FG so don't assume my experience will be yours. If I was you, I'd probably do either the cat or the cat back, but not both.

Some people claim that any exhaust change on a stock tune risks detonation and engine destruction, but personally I think they have read too much interwebs.

On 08/03/2018 at 7:05 PM, Ford Freak said:

whats your plans with the car

 

a bit more info mate geezus

Sorry mate new to this,car has a big plazmaman intercooler and intake muffler delete,was thinking 3. 1/2 inch dump pipe with 150 cell hi flo cat,  1000 cc injectors and a tune for 98 octane.Thoughts???

intake muffler delete doesnt do anything

Didn’t say it did,was just saying that it’s been done