I still have a Gen2 L67 TB and an L27 here to look at again, but I've spent alot of time already trying to figure it out, and have discussed it at length with Don on the phone.

TB and MAF sensor cleaning as you mention, is a good idea for a high-mileage car. I suggest doing it every 50k miles or so from what I've seen on both of my own cars.

That procedure is in Techinfo.

I havent cleaned it out yet, but it is on the list. there Looked To Be A Ton Of Junk In There When I Did The Air Box. I Read The Tech Info On That One. Tis Site Is Great Help!