[dyerkes]

Pat,

If your car does have the US version of the headers (cross-over of the right bank occurs on the transmission end of the engine), than you stand to loose about 40lbs and decrease your spool time by about 700rpms. Dave's gains could only have occurred with a number of mods on top of the headers - cams, free-flow muffler, and higher output turbo. Once you start increasing the HP of your turbo, you better do two things: get a more efficient intercooler (no HP gains, just keeps the charge temps at a reasonable level) and (2) at a minimum, have your AFR settings check to make sure that you aren't running lean with the improved flow that you created with the previously mentioned mods - ultimately (if you decide to stay CIS) you should consider having your fuel head modified by Stephen Kaspar of IA, so that it can provide enough fuel flow at the top end. Don't forget that the stock rod bolts are only rated to the mid 400 HP range, so if you decide to do a significant number of mods you may need to consider having to replace these in your HP equation.

I have first-hand experience with this as I am currently in the process of rebuilding my motor and performing some major upgrades to it.

Good luck!
David
1986 911 Turbo