We did the upgrade to our 98xj w/99 intake and new BBk 62mm, new header,new pipes all the way,new cat, magna flow, k&n high flow.

Get a funny whistle going thru rpms mostly outta 2nd into 3rd.
It's down in the throttle body, changed out throttle still does it, Take off k&n still does it... It's faint with stock tb, But very pronounced with the 62mm.
Anything I should try? no vac leaks that I can find... been re-tightened
Didn't do it w/98 box intake and stock tb. I can't make any difference with it. Searched and searched.. am I missing something?

intake was nice and flat when I checked it, No noticeable cracks or anything.

 

It seems the whistle is common with the BBK 62mm.. Here is just one review from amazon.
4.0 out of 5 starsbbk 62mm tb
By Sam WhiteMoon on May 24, 2013 Verified Purchase I am satisfied with this item. Increased throttle response and a pleasant whistling sound should be expected. 5 stars don't apply because I had to bend the linkage arm so it wouldnt collide with the intake manifold. Expect a trip to the hardware store because the stock machine screws fastening the sensors (not supplied) tend to snap. A cold air intake, high flow cat, and aftermarket muffler compliment this addition niceley.

My Jeepers and creeps 62mm TB had a whistle until I went and rounded off any sharp edges inside the T/b also make sure the gasket is perfect fit to the intake..any gasket hanging out that you can feel it on the inside of the TB will make a whistle..try to trim it if it does have a little hanging out to much. Try to match the TB gasket perfect to the TB and intake..

 

Ya I used a stock gasket because BBK was a little different in size. perfect fit as far as I can tell..
I been told mixed reviews on whistling BBK's and swapped a couple, the one I have now is best, but the one before couldn't handle any massaging as the rpms at idle started to climb with very minimal edging done. iac port had some very sharp edge. I haven't touched this one.

I wouldn't call it pleasant like that review does!
Talked to a local dealer and he said he'd never heard of that before.

When I swap the stock tb back on it's still has a whistle coming from in the Throttle body itself, The 62 just magnifies it even more.
It couldn't be from the intake gasket could it? Brand new gasket.

 

I dont think so,, but there is always a first.. I would start looking for missing vacum nip caps or lose air line But Im sure you have done that.. so hmmm,, The only time I ever had a whistle was with the Jeepers and creepers TB..once I smoothed out the edges it stopped.. So **** Im kinda out of ideas right now..maybe someone else can chime in..

 

Thanks man,
I really don't want the 98 body back on, I Really like what I get from the 99, Minus the whistle