Originally Posted by Hesselrode

If u took an 8 and ported it and did everything like ecu, cobb ap, exhaust, intake, coils, etc, what kind of power would you get from it?

Originally Posted by Hesselrode

I meant with the best stuff you could buy.

Originally Posted by RIWWP

Power Modifications:
From the factory, the 8 is VERY well tuned (mechanically). There are only 2 things you can do for easy power:
- AccessPORT custom tune to remove some of the "safe" parts of the tune
- Removing the naturally restrictive catalytic converter.

Doing the rest of the common upgrades piston cars get (intake, exhaust, pulleys, etc...) nets you MAYBE 5hp. MAYBE. Depending on the brand, alot of them are inferior to the OEM stock system, and plenty cause you to lose power.

If you want power, you have to go forced induction, turbo or supercharger. And you need a starting amount of about $8,000 to $10,000 for a complete set up. If you find what you think is a "deal", please don't get fooled. If you spent $1,500 on your turbo system, you will still spend $8,000 to $10,000 in modifications, errors, swapping parts, getting stuff to finally work right, and probably an engine replacement along the way. If you dont have an AccessPORT, you have very little chance in making it work.

If you don't go that route, then the most you can expect is about 200 whp without a custom engine rebuild, which can run you $5,000+ once you factor in the labor of pulling and reinstalling the engine and the shipping. The advancements in porting work have been slow coming, but they are still moving the needle upwards.
BDC has taken the new top N/A dyno (non-race team funded) posted on 5/16/2011 here: https://www.rx8club.com/showthread.php?t=216762 223whp:

Please note that "heavy" has not been defined as of this edit. The gains are from more than 1 source. Likely full 3 inch headers to tips on the exhaust, entirely unknown what the intake is. The porting work above was mostly on the intake ports rather than the exhaust ports. There was also likely significant improvement in the seal tolerances over factory specs.

Eric Meyer posted his 233hp dyno sheet here: https://www.rx8club.com/series-i-major-horsepower-upgrades-93/233-rwhp-dyno-sheet-218322/
But keep in mind that it's likely his team invested $100,000+ (just a guess) into the R+D of the engine and drivetrain to get it there (including special treatments of the transmission and diff to reduce drivetrain loss)