[grizzly]

just picked up a 1998 jetta tdi.

it's already got a chip, would adding a boost controller help much?

 

[jon applespeed]

Welcome, check out the FAQ called 1000q (1000 answered questions), it is also listed in the stickied post at the top.

To answer your questions, if you already have a chip, a boost controller would help marginally since you have a conventional wastegate style turbo and a electronic solenoid type controller would help keep the wastegate shut until the desired pressure. A spring type manual controller won't be as helpful so I wouldn't spend the money on it. In short, just leave it as is since you say you already have a chip.

 

[miker]

the best thing you can do is install a free flow exhaust.

It will increase noise and emissions but also increase power. Personally, I would install a chip and leave it be. A chip is the best value out there for performance mods

 

[chittychittybangbang]

to give you some ideas, the blitz sbc boost controllers are probably my favorites ecause they use a very large solenoid and can go up to the high boost pressure that diesels see, 36 psi max. however, it also costs $500.

spend your money on a chip first.

 

[jon applespeed]

He said he already had a chip...spend your money on new shocks and mounts/bushings. They are probably worn out on your car if they haven't been changed yet.