I swapped an extra tpi unit to my 91 K2500 pickup and everything ran great until a month later I added a set of headers and new exhaust and I would get a code 32 everytime I would go to and from work. This was a problem for a year and in this time I pulled the intake and cleaned all of the passages, replaced the egr valve, replaced, egr switch, vaccum lines, vaccum selinoid, and retraced all of the wiring. Everything checked out fine and running through the none scan diagnostics everything checked out fine except I was unable to pull the egr open with a vaccum pump with the engine running. So I came up with a fix. I ended up opening up the hole in the egr valve where the vaccum line attahes with a 3/64 punch. This has solved my code 32 for 2 weeks now. I use to get the code 32 two times a day so I am sure it is fine now. I am also able to open up the egr with a vaccum pump or vaccum line at idle and make the engine stall. The wierd thing is that the whole tpi system was on my camaro with slp headers and 3 inch exhaust and I never got a code 32.