IDP Plenum and 74 throttle body
 

On a stock Box S (986)car, would I notice any difference from the seat or not really noticeable without other mods?
Thanks

No. You might notice a slight increase in mid-range torque, but that's it. That combo is best when used with a tune, but I don't recommend a tune on a stock engine. Plus, depending on the tune, you can get some wild fuel / air mixtures. I had a friend with an 09 Cayman that had one of the two famous tunes installed. You could smell raw fuel at the exhaust, which caused headaches from the CEL due to the fuel being sniffed by the 2nd O2 sensor.

I have an IPD plenum and 83mm TB on my Cayman with no tune. If I had it to do over, I'd spend that $1K on suspension parts from Tarrett.

think of it as an expensive sprint booster - small throttle inputs make a bigger difference with the larger throttle body.

you have a 1" water line with a 1" valve - 1/2 water flows when 1/2 open, all water flows when fully open.

now put a 2" valve on the 1" line - all the water flows when only partially open. and no change beyond that.

Let's face reality, engine (performance) upgrades aren't worth it anymore. Most modern family cars with their turbo engines will be a challenge for our beloved classic Boxster. Some goes for the aircooled 911.
Desnorkeling/ PSE / IPD / 74mm TB / +100 octane fuel were "slightly" noticeable all together, but you get used to it so fast...my Sprintbooster was probably the most noticable perfdormance change btw.
...and once an A3 out sprints you and you are having a hard time passing a fully loaded Skoda octavia RS on the autobahn, you know our Boxsters turned into a classic car. Not even mentioning EVs.
Sound wise those upgrades will be a blast.

986 driveability is unrivalled compared to nowadays cars, which have completely lost that analog feel.

+1 on that statement.. On the POC (Porsche Owners Club) They consider these cars a 'momentum car' for which they are awesome at.. :rolleyes: