Tuner's w/ decent power increases?

Ok, new to the forum and am basically looking out of general interest of diesel engines. My mom recently purchased a 2006 VW Beetle with the 1.9L TDI engine. I, on the other hand, own a 2003 F250 with a 6.0L Powerstroke diesel and I have a tuner that added 175hp at the rear wheels. I have only ever messed with larger diesel engines, but was under the impression that most all diesel engines had a lot of hidden power that could be tapped into with a tuner. However, most of the tunes that I've looked at for these TDIs only gain about 30hp on average. I was going to put one in my mom's bug and not tell her and see if she noticed any difference. My question is this though. Is 30hp on a little bitty bug somewhat equivalent to 175hp on a 8800lb 3/4ton pickup? Will a tuner gain MPGs? Also, one thing to consider is that I live in SC so we have no emissions laws or anything like that. So what are my options? Since it's not my car I don't want to spend an ass load, but I think it would be fun to play with if it's something where I'll notice a good power increase and some MPG increases also. Definately don't want to kill MPGs though cause my mom definately wouldn't care about added power over MPG...that's only for the younger guys like me

To see if a 30 HP gain with a 100 HP TDI is similar to 175 HP on an xyz HP Powerstroke, I'd start comparing ratios. Percent gain and weight difference.

On a stock 2006 TDI you're limited to a 30 to 40 HP increase because of the turbo.

A retune/remap is the preferred method, there's going to be a Rocketchip tuning Get-Together in Chapin, SC in January.

Start with a new clutch cause the oem's ones fail on a stock tune.

Say beetle = 2400lb as stock? 30hp is same as about 100hp for the truck, as a rough guess. Will not be too shabby, but as a N/A mate often says "no replacement for displacement" - but then he got a supercharged Jag XJR.... They always go forced induction in the end.

There are a couple plug in boxes for the TDI, but they are nothing like the truck boxes. They fool a couple sensors and you get more power, but it's not as "refined" as a custom ecu remap. You can get a nice tune from several vendors here on the club. Price will be $300 ish for about 30-40 hp at the wheels. It will transform the car IMO.
You could hack out the exhaust for a nicer sound, but this will lead to "boost creep" on your BEW engine. I'd recommend leaving exhaust stock unless the turbo gets upgraded.