Retune Or Wait?

I'd say it's probably OK to wait. Longtubes make more power by getting the exhaust out of the cylinder more completely, and thus pulling in a little bit more intake air. If your tuner has any clue as to what he's doing, he'd have the MAF scaling set so that if the counts go over what he tuned it at (i.e., the motor is bringing in more air than when he tuned it), it'll usually over-compensate and add more fuel than what is needed, resulting in it actually running richer.

Do you have a programmer? If so, can you make any basic changes in the tune? I can on mine, and if it were me in this situation, I'd just add about 2, maybe 4% more fuel just to be sure, and maybe pull a degree or two of timing. Probably won't make any more power with the longtubes this way, but I personally would feel fine running it this way.

Of course, having a wideband to confirm that it isn't going lean would be ideal. And if you EVER hear ANY detonation, back out of it IMMEDIATELY. Detonation, even just a little bit, is what usually blows these engines.

I probably wouldn't worry about it. Do you have a wideband (is a MUST for any FI car IMO)? Just keep an eye on the a/f.