Hi guys. New to this. First post. (Be gentle)

I'm looking to do a service and a few minor upgrades to my 99 Forester GT.
Standard oil, air and petrol filter. Fluid flush and replace (oil, brake, transmission, power steering etc). Then some add ons.

My question is - my fuel filter has 3 hoses coming off it (in, out and purge?) and the replacement filters only have 2 hose fittings?
What should I do?

After its service (timing belt seems fine, accelerater cable tightened already)
I will be adding some extras and upgrades to the stock engine (cat back 3" exhaust and silencer delete only).
- Td04l 13t (replacing stock tr035)
- bellmouth downpipe
- boost gauge
- hks ssq4 bov
- duel stage boost controller
- fuel cut defender
- cold air intake
And I'm sure I'll find a gasket or hose that will need replacing along the way.

Then off to the dyno for a tune.
Any idea on A- a solution to my fuel filter cunundrum?
B- what gains should I expect after the mild upgrades?

Any help appreciated.