New heads or intake manifold

[91LX2Bfast]

Just save up untill you can do both at the same time. Get the 99+ PI heads and intake. If you get 2001+ heads, you can keep your stock valve covers and save some cash. YOu will get all parts for cheaper then the price of only a set of FRPP heads.
Get a 3 or 5 angle valve job and just have some light cleanup porting and you should be pushing 20more hp then a stock 99+ GT. YOu will be running a higher CR because you have different pistons then the 99+ GT's, and thats a great thing for a N/A build up.
Another option is getting the Bullitt intake instead of the stock one. It is almost identicle to the FRPP, although I am not sure how helpful it is one N/A cars.

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1997 Thunderbird 4.6L: Dynomax exhaust, Lightning 80mm MAF with 7" powerstack cone filter, B&M 24,000GVW trans cooler, Inject-Tech chip, KVR Brake upgrade. 15.2 @ 91. Not bad for a 3800lb auto 4.6L

No Longer own: 91 LX 5.0L 5 spd