VERY surprised that a 49 is even around any more???
They're so... 1987-ish. Nostalgic, yes, but "antiquey" & needless.
The Limit LT-61s from John Craig, the 6152s from Fullthrottle
(as well as other similarly sized non-BB & even larger BB-turbos)
have proved over & over years ago that there is no lag
when running properly with the factory D-5 converter.
If you get "lag", it isn't originating w/those units, so it'd be best to look
elsewhere than the turbo or converter for something else to blame for any "lag".
We've owned & ran both turbos mentioned above, with the D-5,
& perpetually pondered :"WHY" anyone would wish to waste
their hard-earned cash on a 49?
[And the answer is: "CUZ MY GRANPAPPY HAD ONE, MAC!!"]
A colossal demonstration of choices from yesteryear
in a combo is to see a GN with a teeny 49, a blingy FM,
the "fabled" 009 injectors, and possibly even with a
crushed 237 FPR.
Threads about 'which turbo" resurrect & perpetuate
myths like front porch lights draw moths.
Here's hoping you get more for your money than a 49 will provide.
Out of all the rich multitude of great choices for an intial-upgrade
turbo, the 49 should not even be showing up on anyone's radar
in 2008. It was superbly superceded years ago.
Help pass the word.