Hi ! Have a 91 Firebird TBI engine (code "E"). At present it has no EGR valve installed. Need a new one. Which kind of EGR valve do I need ? : "P" = positive backpressure "N" = negative backpressure blank = ported Which part number is stamped on yours ? Thx P.

I'm not 100% certain, but I want to say that yours is "positive backpressure." When I still had the 305 tbi in my car (code E), I bought a new egr valve. The PN on the box is EGR1212 (BWD Brand). It also has POS printed on the part. The other reason I believe it to be positive backpressure is that when I put headers on the car and reduced the backpressure, the check engine light came on claiming it was unable to open the egr vavle. From reading the factory service manual, it appears that the egr valve uses exhaust pressure to help open the valve. If the pressure isn't there (like when you have headers installed), it's harder for the valve to open...

Can anyone confirm this?

Hi !

Thx for the reply. Will try it !

Regs
P.

dunno if this is of any help, but i just thought i'll post this for you to look into. there are some more part numbers, including both information about the stock setup as well as egr compatibility with headers.

edit: lol forgot the link
http://www.thirdgen.org/techboard/tbi/390118-what-egr-valve-headers.html