I had a Gen2 SWB 6G72 3.0L engine in Australia. I had headers, a free flow cat and a tuned exhaust - about 2 3/8" diameter. It was VERY noisy above 3250 RPM - effectively limiting my speed to 110KPH. I had no improvement in mileage. Perhaps I got a tiny increase in high RPM response and power. It wasn't worth the expense - and it was way too noisy. I had to get an authorized db test to make it legal - it passed by about 2db.

Last edited by Bernoulli; 07/15/14 05:58 PM.
89 3L V6 5spd SWB, Aisin Manual Hubs, 2 (suspension) seater Raider in Wheeler, OR